Just like to say Hello, brand new to this forum. Am possibly picking up a 1984 Chevy pickup this Friday with a 6.2L so i needed to find out as much info as possible

Just some back ground, the truck as mentioned is a 6.2l 84 Chevy 4x4 heavy half and 3'' suspension lift

Now enough of my ranting and onto my questions

I grew up on the farm and still often go back to help out on the family farm. With that said, being the owner of a truck i have no probaly throwing a hay bale in the back (big round one) or hooking up to a stock trailer. Even around home i have a small trailer i pull with my 2WD S10 when hauling dirt.

I am curious if the 6.2L will be able to handle this rare heavy load. Assuming i don't drive like a teenager when under a load (i am only 17 and often drive my age) i am thinking i should be ok? my other concern, is that if i do get this truck, i need to use it to haul my old project truck (83 GMC half ton) back to the farm...cause well its just to expensive and i got a diesel now :D
this 6.2l would accutally be my 4th truck. ALSO, the only other thing i would put behind it is my dads jet skis or qauds, and i mean come on, my S10 could so it... and this truck being a 3/4 i don't see how it could do to much harm to these engines (specially if i didn't drive my age and drove it properly)

The engine was rebuilt, how long ago not to sure bout the guys thinks it was 50k ago.

My next thing is, the guy says that in the city he can sqeeuze 30 MPG out of this thing.... i looked at him and asked if he thought i was stupid. is this even touchable with these trucks. i mean i can live with even 15 or 16 cause its a hell of alot better then the 5-6 i am gettin in my 4.3L V6 S10

i hope to hear back from y'all soon, cause tonight is Tuesday night... and i am going to look at it on Friday. i have some advice coming back on these engines from two heavy duty mechanics, but what a better place to ask then a forum like this

BTW, this truck is only 1 grand (Canadian, that it makes much of a difference cause our dollar is pretty much on par with the green back)

Yes i am Canadian, but just received me American Citizenship a few months ago :D

It will work but don't expect to be able to reach high speeds. Putting a turbo on will help it out but it still won't be as good as say a Cummins or Duramax.

no no

i would never expect this truck to keep up with my grandpa's 99 cummins or a brand new duramax

and speed is not a issue, specially towing a vehicle i got no problem turning the radio on and enjoying the ride

all i am worrie bout is puttin to much stress on the engine and giving me expensive problems down the road

Just watch the temperatures and put better trans and oil coolers on there.

One important thing. You say its a Heavy Half? What axle ratio is it? What transmission is it? If its the 3.08 / 700R4 combo, I would strongly advise against towing anything heavy with it....

One important thing. You say its a Heavy Half? What axle ratio is it? What transmission is it? If its the 3.08 / 700R4 combo, I would strongly advise against towing anything heavy with it....

and this truck being a 3/4 i don't see how it could do to much harm to these engines

Im guessing its a light 3/4 ton.

Just like to say Hello, brand new to this forum. Am possibly picking up a 1984 Chevy pickup this Friday with a 6.2L so i needed to find out as much info as possible

I am curious if the 6.2L will be able to handle this rare heavy load. Assuming i don't drive like a teenager when under a load (i am only 17 and

30 miles per U.S. gallon is never going to happen. Best case situation with no lift, stock tires, and overdrive - and you might get around 25 MPG on the flat highway. Expect 16-17 MPG mixed driving.
A typical stock 3/4 ton truck with 3.73s and no overdrive will get more like 18 MPG highway at 65 MPH, and drop like a rock when you go faster.

In regard to towing, if geared properly, you can pull almost anything, but even with the correct gearing (3.73 or 4.10) you going to be pulling steep hills at 40 MPH if a heavy trailer is hooked behind. And, you also might have to pull over half way up and let the engine cool down - if on a hot day.

Besides pulling, braking can be a problem with 1/2 tons if coming down long hills with a trailer. 1/2 ton JD5 brakes are not adequate to hold back a trailer if the trailer-brakes fail. 3/4 ton JD5 are just barely adequate, and JD7 better.

One important thing. You say its a Heavy Half? What axle ratio is it? What transmission is it? If its the 3.08 / 700R4 combo, I would strongly advise against towing anything heavy with it....

Well i will defiantly be look into this. How ever, some thing in the back of my mind tells me this guy won't have a single clue

and mentioned a few posts up, my milage will drop like a drop if goin over 65 MPH (104 KM/H for me and any other canucks), how bad we talkin in terms of droppin like a rock

My friend..I owned a 6.2L 92 1500. I got, on the Hwy doing 75mph, MT truck - (120km/hr)... in the 24-26 mpg range...!! and that's no BS. Used to drive to Toronto from Cornwall all the time on the 401. That was on a unit with no mods whatsoever. great motor / great truck, wish I had kept it.

Not sure what the tranny was at the time..others here, would for sure.

stk

US or Canadian gallons? If that is Canadian gallons then it is only 19 miles per US gallon.

US or Canadian gallons? If that is Canadian gallons then it is only 19 miles per US gallon.

There's not a 6.2 powered truck on this planet that's going to get 26 miles per US gallon at 75 MPH. Even 26 MPG Canadian is a stretch at 75 MPH.
Best fuel mileage I ever witnessed, first hand - is with a 1/2 4WD ton pickup - all stock - with 3.08 axles and NP833 overdrive-manual trans - and it got 24 MPG at 65 MPH on a perfectly flat highway and probably a slight wind pushing behind it. 22 MPG is more the usual.
I assume, had it been 2WD it would of done a little better.

Just for reference, my 83 Mercedes car - a 300D with a 3 liter turbo-diesel gets a best of 28 MPG at 65 MPH and drops to 25 MPG at 75 MPH.
My 85 Isuzu 4WD mini-truck with a 2.2 diesel gets a best of 28 MPG at 65 MPH. My 92 Dodge D250 with 3.50 axles, 5 speed manual overdrive Gertrag, turbo-intercooled 5.9 Cummins diesel gets 21 MPG at 65 MPH.
My best diesel Chevy Blazer - with 6.2 diesel, 3.08 axles, and 700R4 auto-overdrive has gotten 23 MPG (US) at 65 MPH. My best diesel Suburban - a 1991 with 6.2, 3.42 axles, 700R4 auto-overdrive gets a best of 21 MPG at 65 MPH. My worst fuel mileage 6.2 - is a 89 GMC 3/4 4WD Suburban with 3.73 axles and TH400 trans -gets 18.5 MPG best at 65 MPH at below 1000 feet elevation and drops to 16 MPG at over 5000 feet elevation at 65 MPH.

for towing another vehicle you can do it with 3.08 gears if your not in a mountainous area. my truck has the 305 gasser so similar power levels to the 6.2 just higher up in the rpm's. i'm running 33" tires and an sm465 manual tranny (no overdrive) and turing roughly 2300 rpms at 70mph (keep in mind my torque/horsepower is not reached until over 3000rpms) and i just pulled a 99 honda crv roughly 300 miles through the texas hill country with no problem. my truck is a heavy half as well.

for towing another vehicle you can do it with 3.08 gears if your not in a mountainous area. my truck has the 305 gasser so similar power levels to the 6.2 just higher up in the rpm's. i'm running 33" tires and an sm465 manual tranny (no overdrive) and turing roughly 2300 rpms at 70mph (keep in mind my torque/horsepower is not reached until over 3000rpms) and i just pulled a 99 honda crv roughly 300 miles through the texas hill country with no problem. my truck is a heavy half as well.

Trick here being the sm465... 3.08 gears is very very hard on a 700r4, put extra weight behind it, you are just waiting for it to burn up, because it will.

Both subjects (MPG + towing) have been discussed so many times it's not even funny. If you do a quick search you will turn up lots of results. Some members have distinctly different opinions and experiences and therefore there has been lots of discussion.

I never understood why there was all the discussion on towing with these trucks... It's an eighties Chevy truck. Yeah, you can tow with it. The eighties chevys were always good for just about anything. Sure, there are better trucks for the job. They are also notably more expensive. If you're looking for a truck in the price range these fall into you won't find a better work truck that gets similar fuel economy.

As far as fuel economy goes I'm not going to get into a discussion about the actual numbers but I will say that in my experience these are just about unbeatable for fuel economy. Considering the size of the trucks they get great mileage.

Here's some facts on my experience on fuel economy with the 6.2... I had a Ford F100 for a while. The truck was plenty healthy with a 302 with a 2bbl carb and an automatic tranny. 97K miles on it. At the time I was driving approximately 23-24 miles one way to work on 55 mph two lane. Four stop signs during the trip. That truck used 5 US gallons of gas every single day when I did that. 20 gallon tank. I'd literally have to fill it up every other day. I drove my 3/4 ton GMC with the 6.2 on the same trip for quite a while. I would fill that every 6 days and it took almost exactly 11 gallons every time. The 302 was completely gutless (even when run hard) compared to the 6.2. Draw your own conclusions...

Trick here being the sm465... 3.08 gears is very very hard on a 700r4, put extra weight behind it, you are just waiting for it to burn up, because it will.

I towed many miles with two Chevy Blazers with 6.2s - both with 3.08 axles - but one has the TH400 trans (with mechancial modulator) and the other the 700R4. Never had any trans. trouble with either - but - whenever I use the 700R4 for towing, I unplug the wire-harness from the trans so the converter doesn't lock up. If kept out of overdrive, it's about the same durability as a TH350. Also, I'm talking about trailer weights under 5000 lbs. Last long trip I took - was with the 86 Blazer with 700R4 and 3.08s - and pulled a 4000 lb. camper-trailer all over Michigan, New York, and Canada - with many mountains. Climbed some hills at 30 MPH top speed - and got an overall fuelmileage - for 2800 miles - of 13 MPG.

I did the exacty same trip previously, with a Chevy 1/2 van and 350 gasser - pulling the same trailer and averaged 9 MPG for the entire trip.

Did the same trip with my 94 F250 Ford with 7.3 turbo diesel - with a slide-on camper instead of the trailer - very heavily loaded - and got 15 MPG.

I'm still searching for something better. This year it will be my 92 Dodge with 5.9 Cummins, and then I'm going to try it with latest 6.2 I'm putting together - 83 Blazer with a Chalet pop-up camper body, a turbo 6.2, and 3.42 axles with a beefed-up 700R4.

For the sake of disccusion we are talkin US gallons

Never had any trans. trouble with either - but - whenever I use the 700R4 for towing, I unplug the wire-harness from the trans so the converter doesn't lock up.

That's not a good idea.

Driving with a non-functioning torque converter lockup may be easier on the hard parts in the tranny but everything else will suffer. It causes the transmission to overheat. If you drop it into drive rather than overdrive that will make the tranny live better but disconnecting the torque converter lockup isn't a good thing to do.

That's not a good idea.

Driving with a non-functioning torque converter lockup may be easier on the hard parts in the tranny but everything else will suffer. It causes the transmission to overheat. If you drop it into drive rather than overdrive that will make the tranny live better but disconnecting the torque converter lockup isn't a good thing to do.

Yeah, I had a guy in a trans shop tell me that 135,000 miles ago and my trans still works fine. I originally got the idea from my wife's 1986 Jimmy with a 2.8 V6 and 700R4. The lockup went bad and made an awful screeching noise whenever it locked up. So, with a "nothing to lose" attitude, I unhooked the wire harness - put another 80,000 miles on it, and then sold it - with the trans still working fine.

In regard to my 86 K5 diesel Blazer, seems it has lasted a lot longer than many others.

I'll ask you the same thing I asked the transmission guy years ago. Why is a 700R4, with lockup-converter unplugged, supposed to heat up more than a TH350 or TH400 that never had one to start with?

with my 84 1/2 ton 4x4 with a 2.5" lift 4.11 gears 700r4 i got 19.5 goin 85 topped out with cruise control on. i had 31's on though if i had 33's it probably would of been more like 17

I'll ask you the same thing I asked the transmission guy years ago. Why is a 700R4, with lockup-converter unplugged, supposed to heat up more than a TH350 or TH400 that never had one to start with?


Older model 700R4's this is VERY bad for them. Something about how the plumbing is done inside of them makes the fluid heat up rapidly when not locking up properly. This from my research when I put the 700R4 in my M1009.

My point about the 700r4/3.08 combo is... Its a very bad combo for towing. can you do it yes. Is it Ideal no. It WILL cause you grief eventually. (If all is left stock).

Older model 700R4's this is VERY bad for them. Something about how the plumbing is done inside of them makes the fluid heat up rapidly when not locking up properly. This from my research when I put the 700R4 in my M1009.

My point about the 700r4/3.08 combo is... Its a very bad combo for towing. can you do it yes. Is it Ideal no. It WILL cause you grief eventually. (If all is left stock).

Like I said previously, I've heard that for years - but don't believe it (about the heat without lockup). I've put close to 140,000 miles on mine since I did an "el cheapo" rebuild on it. And, the wire harness has been unplugged ever since - except for when I take it on long highway runs. Around here, in the mountains of New York, having the lockup working does not give me any better fuel mileage - not even on the nearby Interstate. That, because of all the hills causing unlocks/downshifts. On long flat trips though, the lockup makes a substantial difference in better fuel mileage.
Also drove my wife's 86 S15 Jimmy for many miles, unplugged and it never hurt a thing.
In regard to hotter trans. temps? I don't believe that either. I'm sure the 700R4 gets hotter without the lockup than it does with. But, I do NOT believe it gets any hotter than any of my vehicles with TH350s or TH400s (or Ford C6). I don't have any trans. temp gauges hooked up, but I certainly know what a hot trans feels like through the floorboards - and what burnt trans. oil smells and looks like.
Seems to me, that a person WITH the lockup hooked properly would consider 140,000 miles a pretty good life for a 700R4 in a truck. Mine has that much, still works fine, and people are telling me I'm hurting it?

In regard to towing in general withi 3.08s - yeah they're awful - as compared to 3.73, 4.10s, etc. And, if you up the torque and horsepower - and put it against those little gears (usually 10 bolt rears), they don't hold up all that well. That being said, for light trailers and/or flat highways, they work okay. I towed a large boat and a camper trailer for many years with 3.08s. It's all kind of relative. When I was a teenager, most people were pulling their boats and camper trailers with family cars (not trucks of any sort) and managed to get along. If you could go back to the 60s - and give one of those people a K5 diesel Blazer with 3.08 axles and a tow-hitch -they'd think they really had something powerful.

I agree with your luck... When I said 'later' it was for pre-86 I believe (dont recall for sure, but think thats the year change for it)

Yeah, I had a guy in a trans shop tell me that 135,000 miles ago and my trans still works fine. I originally got the idea from my wife's 1986 Jimmy with a 2.8 V6 and 700R4. The lockup went bad and made an awful screeching noise whenever it locked up. So, with a "nothing to lose" attitude, I unhooked the wire harness - put another 80,000 miles on it, and then sold it - with the trans still working fine.

In regard to my 86 K5 diesel Blazer, seems it has lasted a lot longer than many others.

I'll ask you the same thing I asked the transmission guy years ago. Why is a 700R4, with lockup-converter unplugged, supposed to heat up more than a TH350 or TH400 that never had one to start with?


I honestly do not know the answer to your question. I will look it up and ask a few tranny guys to try and find out...

I do know there is truth to the "myth". I had this happen on a truck I was working on not long ago... The lockup wasn't working and we tried driving it that way... The tranny worked fine until you drove for a good 15 minutes or worked it hard and then it would start shifting funny and distinctly slipping. If you stopped for a minute or drove gently it would shift normally afterwards and would then start to slip again. Fixed the lockup and never had a problem with any of that again. Did a little research and found that a non-functioning converter lockup is a common source of problems and transmission failures. This particular transmission was out of an '88 G-10 van.

As far as your tranny goes, if those miles with the converter unlocked were mostly highway miles maybe it wouldn't hurt the tranny. For one thing it wouldn't heat up as much just cruising and for another it wouldn't be shifting at all so it wouldn't have a chance to slip.

Well first off i would like to apoligize for asking a repeating question. I do know how annoying it can become

Although as i scroll back threw the forum i have yet to find one thread with this much dicussion and this much information

I have learned a hell of alot in a matter of 2 days, and i don't even own a diesel yet, lol

would just like to thank every one for there comments and will keep you posted whether or not i pick this truck up

Scott

Dude!
If you can only get 5-6 mpg out of a 4.3 S-10 then you have a serious maintence problem or a foot heavier than my wifes rear-end!:D

Gary

Dude!
If you can only get 5-6 mpg out of a 4.3 S-10 then you have a serious maintence problem or a foot heavier than my wifes rear-end!:D

Gary

lol no no.. i am 17...and do drive like i am 17, but i should still be getting better

its not quite as bad as 5-6 MPG, but for awhile there it was. If i pick up this diesel, i am sending the S10 to the shop, tellin them to fix it (sick of screwing around with it) and jsut paying the bill

going to cost me alot more in the long run i just wanna get rid of it

I honestly do not know the answer to your question. I will look it up and ask a few tranny guys to try and find out...

I do know there is truth to the "myth". I had this happen on a truck I was working on not long ago... The lockup wasn't working and we tried driving it that way... The tranny worked fine until you drove for a good 15 minutes or worked it hard . . .

As far as your tranny goes, if those miles with the converter unlocked were mostly highway miles maybe it wouldn't hurt the tranny. For one thing it wouldn't heat up as much just cruising and for another it wouldn't be shifting at all so it wouldn't have a chance to slip.

I suspect that in your case, there were other things wrong with the trans.

Any torque-converter is an oil heater - period. A torque-converter slips - all the time - even at cruising speed. A lock-up converter - when "locked" is NO longer a torque converter.
My point being, that any auto-trans without a lockup converter - e.g. a TH350 or TH400 - makes heat. When I was working as a heavy-equipment mechanic, several tractor companies e.g. Case - started selling farm tractors and bulldozers with torque-converter drives. They quickly became nicknamed as "oil heaters" - that because they ran so hot and required large radiators and upgraded cooling systems.

In the case of my 86 Blazer that I've run for years with the converter wire-harness unhooked - it gets driven just as much on back mountain roads, and farm fields, as it does on highways. The only highway near me - Interstate 88 passes through the mountains with many steep climbs. With the wire-harness plugged into the trans - and in overdrive position - it labors on hills, and shifts in and out of OD. With the harness unhooked - it gets just enough torque-converter slippage at 65 MPH to stay in 4th without needing to downshift - i.e. it drives much nicer. This is due to having the 3.08 axles. I have another diesel Blazer - and also a diesel Suburban - both with the 700R4 but both also with the 3.42 axles - and they work fine on the same highway with the trans. plugged in. The 3.08s with overdrive hooked to a 6.2 is not adequate to maintain 65-75 MPH on steep grades with the converter locked.

I still don't believe that a healthy 700R4 run with the wire-harness unhooked - suffers any worse from heat than an older TH350 or TH400.
With the high-heat-warnings I've been hearing, there would have to be a built-in hydraulic leak causing excess heat when not in lock-up mode - and that makes absolutely no sense to me.

I suspect there have been 700R4s that suffer some type of problem that causes the lockup not to work properly along with other issues - but this has nothing to do with "cause and effect" when unhooking a lockup with a healthy transmission.

Also, the reason why I unhook the harness - instead of just running in 3rd gear position - is so I can get 4th without the lockup. It has worked nicely for many years and miles. I've been wanting to install a simple switch on the dashboard - instead of going underneath to unplug - but have never gotten around to it yet. Years ago, many companies sold the switch-kits.

Maybe you had big cooler on your 700R4? as we all know, TC's work by slipping and this creates a ton of heat, locking up the TC reduces the temps by a huge margin but if its going in and out, that just does damage.

My van averages 17 mpg, I am happy with that as my old 75 B250 gets 9-10 mpg on a good day. Towing my trailer is a nightmare, no power so the 3.73's and turbo will fix that, :D

For mileage I get:
15 towing 6000 lb as fast as the truck will go (55 to 70)
15 to 17 in the city. 12mpg when my wife drives it.
24 driving 60 to 70
28-29 drafting off a larger truck.
Those are with virginia gallons. All the used motor oil and vegetable oil also accounted for as gallons of "fuel".
I have "standard gear ratio" gears. 3.08? Maybe.

Yeah, I had a guy in a trans shop tell me that 135,000 miles ago and my trans still works fine. I originally got the idea from my wife's 1986 Jimmy with a 2.8 V6 and 700R4. The lockup went bad and made an awful screeching noise whenever it locked up. So, with a "nothing to lose" attitude, I unhooked the wire harness - put another 80,000 miles on it, and then sold it - with the trans still working fine.

In regard to my 86 K5 diesel Blazer, seems it has lasted a lot longer than many others.

I'll ask you the same thing I asked the transmission guy years ago. Why is a 700R4, with lockup-converter unplugged, supposed to heat up more than a TH350 or TH400 that never had one to start with?When I had my 700R4 rebuilt that was in my '85 6.2 Sub the IP position switch wouldn't allow it to lock up at all-the trans temp on the highway, on flat ground, in the winter averaged 180*-after rebuild, with the manual TCC switch on, it averaged 130*!!! The locking coverters are built to lock, slip if they don't, and need a switch to lock them up in 3rd gear-otherwise they'll run so hot they'll turn BLUE-and are wasting power & fuel in the process! The turbine fins in the TH350 & TH400s were made to slip a lot less under load (although they still slip a little).

For mileage I get:
15 towing 6000 lb as fast as the truck will go (55 to 70)
15 to 17 in the city. 12mpg when my wife drives it.
24 driving 60 to 70
28-29 drafting off a larger truck.
Those are with virginia gallons. All the used motor oil and vegetable oil also accounted for as gallons of "fuel".
I have "standard gear ratio" gears. 3.08? Maybe. You probably have 3.42-1 gears, would be "GU4" RPO code in your glovebox, your mileage #s are almost exactly what my '85 C1500 700R4 Sub would get (which is why my thirsty '94 is getting a 6.2 to replace it's worn 5.7 gas motor)

Meb's right, I've removed several 700's over the years and found a "blue" convertor. After checking, the TCC had become disabled, for various reasons. Most trucks that had this problem were lt. duty 1/2 tons with high rear axle gears. Most were used on farms and highways, not on freeways. Some simply had the plug pulled off the trans case pass-through connector accompanied by mud, grass and sticks/limbs jammed up between the case and the lt. exhaust pipe.

I love these mileage discussions. You can make the numbers say anything you want, just like the Government does with our tax dollars. My '64 Dart slant six got over 80 miles per gallon of gasoline burned when the CNG (compressed natural gas, two tanks in the trunk, low pressure 2400 psi, equal to 8 gallons of gasoline, I work for the local gas company) system was operational.

It got lots of laughs when the locals opened the hood but was the most fuel efficient vehicle I ever had. I was paying the company $.94 pre therm (roughly 1.1 gallons equivlent) which included a compressor site use fee of $6 per month, when gasoline was $1.85/gal.

The locking coverters are built to lock, slip if they don't, and need a switch to lock them up in 3rd gear-otherwise they'll run so hot they'll turn BLUE-and are wasting power & fuel in the process! The turbine fins in the TH350 & TH400s were made to slip a lot less under load (although they still slip a little).

I don't believe it. All fluid-drive torque conveters slip when not locked up - they are basically just fluid couplings - and they all make heat when slipping. As long as the cooling systems does not allow that heat to pass a certain threshold - there's not a problelm.

Yes, of course a torque-converter in lockup mode makes less heat - but so what?

As far as I can tell - my 700R4s with the lockup "unhooked" slip at the same rate as the older TH400s do - around 10-12% at cruising speed.
Torque converters are rated by stall speed - and the converter stall speed for a 6.2 diesel TH400 and a diesel 700R4 are usually the same. Just read the letter code off the converter.

Any transmission and/or torque-converter can be fried from too much heat - with lock-up or without. If you're going to be doing any heavy towing with a 700R4 - it needs to be unlocked anyway - an will make the same heat as a TH400 - no more and no less.

When I had my 700R4 rebuilt that was in my '85 6.2 Sub the IP position switch wouldn't allow it to lock up at all-the trans temp on the highway, on flat ground, in the winter averaged 180*-after rebuild, with the manual TCC switch on, it averaged 130*!!! The locking coverters are built to lock, slip if they don't, and need a switch to lock them up in 3rd gear-otherwise they'll run so hot they'll turn BLUE-and are wasting power & fuel in the process! The turbine fins in the TH350 & TH400s were made to slip a lot less under load (although they still slip a little).

My 700R4 runs MUCH cooler with the lockup switch on, no doubt about it (similar results to Meb's). The trans shop also made me an offer I couldn't refuse: No wiring harness, No warranty. I also don't tow heavy stuff, drive 85mph, or abuse the old truck.

Any transmission and/or torque-converter can be fried from too much heat - with lock-up or without. If you're going to be doing any heavy towing with a 700R4 - it needs to be unlocked anyway - an will make the same heat as a TH400 - no more and no less.


Exactly but you want it locked up when towing if the engine isn't lugging or dropping in and out of LU. Less heat is produced, the converter isn't slipping and thus the powertrain is more efficient.

I don't believe it. All fluid-drive torque conveters slip when not locked up - they are basically just fluid couplings - and they all make heat when slipping. As long as the cooling systems does not allow that heat to pass a certain threshold - there's not a problelm.

Yes, of course a torque-converter in lockup mode makes less heat - but so what?

As far as I can tell - my 700R4s with the lockup "unhooked" slip at the same rate as the older TH400s do - around 10-12% at cruising speed.
Torque converters are rated by stall speed - and the converter stall speed for a 6.2 diesel TH400 and a diesel 700R4 are usually the same. Just read the letter code off the converter.

Any transmission and/or torque-converter can be fried from too much heat - with lock-up or without. If you're going to be doing any heavy towing with a 700R4 - it needs to be unlocked anyway - an will make the same heat as a TH400 - no more and no less. Don't want to start a big argument about it-but when I got my 700R4 (not locking the TCC) rebuilt, I drove it about 175 miles to the guy who rebuilt it-when he pulled the tranny out, the converter was so hot that it would burn your hands for 2 HOURS after he removed it!!! One of the 700R4's weaknesses is that the converter wire passes thru a 4th gear pressure switch that prevents the converter from locking up in anything but OD-which uses a big friction-lined clamp to (try to!) clamp a rotating drum in OD (think one of those old-fashioned weight loss machines that had the big leather belts)-also the lower engine speed in OD leads to slower (really insufficient) fluid circulation when towing. If you look @ Bowtie Overdrives or another of the tranny buildup sites, you'll see that there are a LOT of perf upgrades for the 700R4, a guy I used to work with runs a big block Nova with a 700R4, routinely in the 10s in the 1/4, hasn't blown it up yet-they CAN be built to last! IMHO, the 700R4 (and the later 4L60E) has a lot more in common with the TH350 than anything else-which means stick to light duty towing (I know I am!!!)

So how do you tow with a 700R4? I guess 3rd gear is towing gear, but I can lock up mine in 3rd as well as in 4th. Shouldn`t I lock it when towing and let it get (too) hot? Or should I lock it, but then it will break (because it`s locked)?

Besides, how comes that almost everyone buys a truck with an automatic transmission instead of a manual though the autos are so horribly troublesome?

So how do you tow with a 700R4? I guess 3rd gear is towing gear, but I can lock up mine in 3rd as well as in 4th. Shouldn`t I lock it when towing and let it get (too) hot? Or should I lock it, but then it will break (because it`s locked)?

Besides, how comes that almost everyone buys a truck with an automatic transmission instead of a manual though the autos are so horribly troublesome?

The automatics are NOT "troublesome" in general. The TH400 or TH475 is a very HD auto trans and holds up just fine under severe duty. Besides being the HD option in 3/4 Chevy trucks and Suburbans, it was also used in tow trucks, motorhomes, etc. The 700R4 is a different story; it was never intended, in stock form, for heavy use.

Not all manuals were intended for heavy use either. The NP833 (OD four speed manual) and the NV3500 five speed manual) are not meant for heavy work and more then the 700R4 is.

I'm not sure how to comment on the "too hot to touch" stories. Yeah, engines and transmissions get hot - even when working fine. Try touching any engine or transmission after a long trip. In regard to the 700R4 - I've towed many miles, for many years with NO lockup and suffered no ill effects. I will say - there's a big difference between a healthy 700R4 being run with the lockup intentionally unhooked - and a 700R4 with problems and a slipping lockup clutch.

There is no difference in torque-converter operation itself and heat - between the units with lockup and without. Without lockup, they slip 10-12%, they make some heat, and the cooling systems for either are the same, etc. In regard to durability - a 700R4 is, in duty-class, a TH350 with OD and lockup added. There is also a TH350C that just has the lockup but no OD. The lockup clutch itself is the weakest link, which makes the plain TH350 a bit more durable. In stock form, the 700R4 was never meant for heavy towing. The heavy-duty "tow rated" auto transmisson late 80s was the TH400.

The automatics are NOT "troublesome" in general.

It appears to me like they are. In Europe, automatic transmissions are an exception, almost all vehicles have manual transmissions. You can get autos as an option on some vehicles, but you usually pay a lot extra for that.

But nobody there who has a manual transmission ever worries about it. They just work fine, they don`t overheat. They last at least 100k miles towing only and at least 190k when not --- and you can tow at full throttle and get full power with them. They require no maintenance while you keep changing oil and filters on the automatic transmissions ever so often.

Automatic transmissions slip the most when you would need the power the most. They generate a lot of heat and eventually overheat and fail. They make you loose a lot of power before they lock up, but when you demand more power, they just unlock and you loose it again. They severely slow you down when trying to tow up a hill. When driving a vehicle with an auto, I`m constantly worried about it.

I`ve had the Tahoe for about 4 years, almost 100k miles. I never floored it and was never hard on it for not to brake the transmission. I kept changing oil and filters and installed a deep pan for $$$. I`m glad it didn`t fail, but it was a real spoiler. (It seemed to be still fine when sold at about 158k miles.). But I even sold a vehicle --- which had a 4L80E like the Tahoe --- which was perfectly fine other than the transmission seemed to act up and I didn`t want to spend the $$$ to rebuild it.


Within about 20 years, I owned 13 vehicles. 7 had manual transmissions, 6 had autos. None of the manual transmissions ever gave me any problem and I worried about none of them, but all of the autos were troublesome in one or way or another and made me worry. One of the autos even had to be rebuild for $$$ and still gives me trouble, and I keep worrying about it (the 700R4 in the Suburban).

Now it seems that you basically can`t even tow with it because the 700R4 is generally just too weak for that. And I`ve been reading somewhere here that the 700R4s are rated for about 6000 pounds GVWR. I have yet to find a scale, but the title of the truck says empty weight is 5500 pounds --- but I`m guessing it`s at least 6000.

Automatic transmissions ARE troublesome. That makes me wonder why people buy them. This time, I wanted to get a truck with a manual tranny, but they are simply not available here because people buy automatic trannys. But why? They kinda suck and cost big money.

It appears to me like they are. In Europe, automatic transmissions are an exception, almost all vehicles have manual transmissions. You can get autos as an option on some vehicles, but you usually pay a lot extra for that.

But nobody there who has a manual transmission ever worries about it. They just work fine, they don`t overheat. They last at least 100k miles towing only and at least 190k when not --- and you can tow at full throttle and get full power with them. They require no maintenance while you keep changing oil and filters on the automatic transmissions ever so often.

Automatic transmissions slip the most when you would need the power the most. They generate a lot of heat and eventually overheat and fail. They make you loose a lot of power before they lock up, but when you demand more power, they just unlock and you loose it again. They severely slow you down when trying to tow up a hill. When driving a vehicle with an auto, I`m constantly worried about it.

I`ve had the Tahoe for about 4 years, almost 100k miles. I never floored it and was never hard on it for not to brake the transmission. I kept changing oil and filters and installed a deep pan for $$$. I`m glad it didn`t fail, but it was a real spoiler. (It seemed to be still fine when sold at about 158k miles.). But I even sold a vehicle --- which had a 4L80E like the Tahoe --- which was perfectly fine other than the transmission seemed to act up and I didn`t want to spend the $$$ to rebuild it.


Within about 20 years, I owned 13 vehicles. 7 had manual transmissions, 6 had autos. None of the manual transmissions ever gave me any problem and I worried about none of them, but all of the autos were troublesome in one or way or another and made me worry. One of the autos even had to be rebuild for $$$ and still gives me trouble, and I keep worrying about it (the 700R4 in the Suburban).

Now it seems that you basically can`t even tow with it because the 700R4 is generally just too weak for that. And I`ve been reading somewhere here that the 700R4s are rated for about 6000 pounds GVWR. I have yet to find a scale, but the title of the truck says empty weight is 5500 pounds --- but I`m guessing it`s at least 6000.

Automatic transmissions ARE troublesome. That makes me wonder why people buy them. This time, I wanted to get a truck with a manual tranny, but they are simply not available here because people buy automatic trannys. But why? They kinda suck and cost big money. Part of the reason automatic trannys are so popular is that the dealers order their stock largely with automatics to improve lease resale values & make their inventory move quicker. When I bought my Dodge (which is a HO Cummins and was only available with the 6 spd. manual) I only wanted a manual-it does all the heavy duty towing (cars, camper, etc.). I've had the same problem as you-even with regular maintenance, I've had trouble with every automatic trans I've EVER OWNED-many new vehicles (such as the newer Subs & Tahoes) haven't been built with a manual for many years, GM just thinks that soccer moms don't want to have to shift them! My '94, when it gets the 6.2 transplant, is going to (probably) run the 4L60E, with a deep sump trans pan & temp gauge, a light to monitor the converter lockup, and 2 transmission coolers-and it isn't even going to tow anything heavy. I still think, if you used common sense, rewired your torque converter clutch to allow lockup in any gear, monitored your temps closely (never over 180F), and used an external cooler, towing (in 3rd, NOT OD!) of up to 5000 lbs would be OK. The reason why I'm not using my 4L80E (which actually doesn't seem in bad shape) is the lower OD ratio and weak OD sprag design-they can't tow in OD either, and I'm shooting for maximium MPGs with the Sub, which only has 1/2 ton rear end & springs anyway.

Part of the reason automatic trannys are so popular is that the dealers order their stock largely with automatics to improve lease resale values & make their inventory move quicker.

Yes, that seems to be the case and also the reason why it's hard to find small-engine economy versions of many vehicles. Dealers only want to stock the more powerful, more "fun to drive" vehicles. I've encounted this when trying to replace my wife's winter daily driver. She absolutey has to have AWD or 4WD where she goes. We've used Subarus for years - but now - even with Subs it hard to find bare-bones cars with small 3 or 4 cylinder engines and standard-shift. Most that I come across are automatic and V-6 (or the larger 2.5 four) and all are full time AWD now - no more part-time 4WD. Same with engines in Jeep Cherokees. Supposedly, there was a 2.5 four-cylinder model made with a 5 speed manual - but I've yet to come across one - not even on Ebay.

In regard to automatics versus standard shift? I think there's been a lot of apples to oranges comparisons here. I'd like to hear some specifics. There seems to be comparisons made between some very HD manuals compared to light-duty automatics. In my experience, standards certainly are not trouble free. I've had to replace many a clutch, clutster gear, syncronizer, input-shaft, etc. in manual setups. My first job as a mechanic was in a HD truck garage - and many of our repairs were of clutches and manual transmissions. Many of the older sliding-gear (no synchros) tranmsissions, we have to pull gears and sharpen them to get them to shift again. I've also worked as a fleet mechanic for small trucks - and in some cases - the automatic trucks held up better that the manual-trans counterparts. Torque-converters are easier on engines because they are torque-limiting. And, some HD autos held up just as well or better then standard units. One case is point is the TH-400 or TH-475. It is meant to be comparible to the M465 heavy-duty manual in durability. And, in many cases the TH400 will outlast the HD manual setup before any teardowns are needed (such as a new clutch). My 87 3/4 ton Suburban towed a livestock trailer since it was new - and made it to 390,000 miles before the TH400 trans needed a teardown. It now has 540,000 miles the trans still works fine. My neighbor did the same type of work with his 88 Chevy one-ton with a four-speed HD manual. He put two clutches in before he hit 80,000 miles and then a snap-ring let loose in the transmission countershaft and caused quite a bit of damage. The trans had to be pulled and rebuilt. Ironically, the truck he had before the 88 was a 76 with a four speed manual and he had much less trouble with it. In the early 80s, I drove a Ford one-ton service truck with a C-6 auto and a 6.9 diesel. I beat the hell out of it, and nothing ever went wrong with it other than normal maintenance stuff. It had well over 150K of very hard miles when we sold it. At the same time, the other road-mechanic in our shop drove a 1 ton Chevy with a 350 gas and HD four-speed manual. It had several cluthes put in before 100K miles, and the trans was removed twice for repairs.
In regard to this forum and talking about transmissions and 6.2 diesels? I don't know of any bad stories about the TH400s or TH475s. The trans is one of the few that worked perfectly since it first came out and lasts a very long time. It got it's start to be used in big-block Buick Riveras and had a two-stage torque-converter for the first few years. It has been used in huge motorhomes, school buses, tow trucks, etc. It was bulletproof right from the start, unlike the TH350, and the 700R4 which were both disasters at first - and then got somewhat patched up as time went on.
Now on the subject of manual transmissions - many were and are - crap. Granted, the SM465 is very rugged trans - except for some weak spots that got added mid-80s. Same with the NV4500. But, take the MY6 four-speed manual with overdrive that was installed in many Chevy 1/2 tons - it's rare to ever hear of one lasting 100K without a teardown. Same with the three-speeds, and same goes for the NV3500s if worked - especially if used with V-8s. Back in the 60s and 70s - seems all we did was replace manual transmissions in muscle cars - Muncie M21s, M22, Saginaws, Borg-Warner T-10s, Ford top-loaders, etc. They all had short lives when used hard. Early 70s, a friend of mine inherited a "family car" - a Chevy Impala with a 396 and a TH400 trans. We mocked him mostly because it was an automatic. Well, his stock "famly car" beat my 65 GTO with a 389-tri-power, 4.33 axle, and a M21 four-speed manual. And, to add insult to injury - I blew two transmissions in it, while his automatic never skipped a beat.
My point here is - there are bad automatics and bad manuals. With the Chevys - many seem to compare the best manual GM ever made - to light-duty automatics which is nonsense. In regard to the mention of European cars and automatics being a rarity? Well, the European cars still have fuel efficiency and economy pricing in mind. That's why they have all kinds of neat little turbo-diesels there too - that so far, we can't use in the US m(any of those little turbo diesels are made by GM and Ford).
I still prefer a manual for heavy work - but that because of wider gear range - not the durabilty. My Cummins-diesel 92 Dodge has a Gertrag five-speed which is - as far as I can tell - the best manual transmission I've ever had in my life. Full synchro in all five gears, very durable, and a very wide range.

Every thing has its limit.
In the towing world standards hold up real good because they don't fall into the heat trap where they build more and more heat. The autos also do well as long as they are used with in limits.
Now if you look at guys who drag race cars, a lot of those "good" 5 speeds don't hold up. It starts with the 3rd gear starting to go, then all gear start grinding and it goes to hell form there.

I say if you have an auto put an over sized cooler on it and put a large hydraulic filter in the cooler line. Like I did.
Then just like that you have prevented 95% of what kills auto transmissions (Heat and dirty fluid). Now you just have to let it fail due to old age and it should give you plenty of warning be for it gives up.

Well, they built some of these trucks with 700R4s from factory. How could they ever do that?


Oilpan4, what filter and cooler are you using, and how did you install it? I`m thinking of keeping the aftermarket cooler on mine but change the lines so that the oil runs through the side tank in the radiator as well (if I can get fittings for that). But I don`t like the idea of all the hoses that could become leaky so easily.

I bought a new hydraulic filter set off ebay with a few extra filters. I have never seen filters like this, they are like a real big oil filter and hold about 1.5Qt. They were advertised as 15micron absolute and 10micron max.
I installed the hydraluic filter in line with the cooler lines. I need to redo my lines because some of there were kind of riged.
The filters are full flow and the filter head unit has a built in by-pass if it gets cloged. The cooler is what I belive to be a U-haul installed medium sized cooler, it was on the truck before I bought it.
The filter is on the discharge line form the trans, I figured hot fluid would be easier to filter, the filter head also has a boss for a temp sender/pressure port and if the cooler has flow going through it all the time I plan to install a temp gauge sender on the filter head.

I belive my filter may have saved my transmission because my wife didn't bother to check the fluid for 3 months and drove it for a few days gravely low on fluid :banghead: . The jerky and sliply operation along with it not shifting out of 2nd gear tiped her off that some thing wasn't right :duh: :think: :cussing: :shootself . I had her add fluid and every thing seams to be ok now.

put Allison in it and put the pedal down got luck killing the allison with the power of a 6.2

The 6.2 would not kill it but I bet a womans touch could.
Would it even bolt up?
If I was looking for a huge up grade I would most likely get a 4L60E and a TCI controler.

I bought a new hydraulic filter set off ebay with a few extra filters.

Hmmm, sounds like a very nice setup :) Maybe I should look out for something like that. Hmm ...

Hmmm, sounds like a very nice setup :) Maybe I should look out for something like that. Hmm ...

I'll bet that FleetFilter in Brenham, one of the sponsors, could fix you up. Good prices too.

www.fleetfilter.com (http://www.fleetfilter.com)

Peyton

Well, they built some of these trucks with 700R4s from factory. How could they ever do that? The fact is, the only ones built w/the 700R4 were 1/2 ton pickups & Blazer/Suburbans-they were looking for MAXIMUM mileage, that was the whole purpose of the 6.2 (& the ill-fated Olds 5.7 before it). If you want to tow with one, wire it to lock in 3rd, add on the extra cooling capacity, closely monitor the temps, or be prepared to buy a new one. BTW, the 700R4/4L60E has a .70 OD drive ratio vs. the 4L80E's .75-that is a major contributing factor to the no towing in OD-my '94 C1500 actually has a door jamb sticker that states that.

The fact is, the only ones built w/the 700R4 were 1/2 ton pickups & Blazer/Suburbans-they were looking for MAXIMUM mileage, that was the whole purpose of the 6.2 (& the ill-fated Olds 5.7 before it).


Did sacrificing reliablilty for mileage pay out for the customers? Mine had a TH400 from factory, but someone replaced it with a 700R4. Does it really make that much of a difference in mileage to even be worthwhile changing from a TH400 to a 700R4?


If you want to tow with one, wire it to lock in 3rd, add on the extra cooling capacity, closely monitor the temps, or be prepared to buy a new one.


Well, it`s wired like that (in a bad way that needs to be changed), and I need to do something about the cooling. And I`d install a trans temp gauge if I had an idea how to do that --- I need some kind of a T-fitting since I can`t screw the temp sender into one of the hoses.


BTW, the 700R4/4L60E has a .70 OD drive ratio vs. the 4L80E's .75-that is a major contributing factor to the no towing in OD-my '94 C1500 actually has a door jamb sticker that states that.Don`t tow in 4th gear with a 4L80E.

Hmm, if I think of it, it`s the same point again: Use a manual transmission instead of an automatic, and you can set it up for maximum mileage. Use a manual, and you don`t have problems with overheating, cooling and wiring. Use a manual, and you can tow in the highest gear (for maximum mileage). And you don`t have to worry about the transmission.


Peyton, fleetfilter looks interesting, thanks!

Does it really make that much of a difference in mileage to even be worthwhile changing from a TH400 to a 700R4?


It makes very little difference unless you do a lot of light-load flat highway driving. One a long, fairly flat trip - my Blazers with 3.08 axles and TH400 trans get around 20 MPG. My Blazers with same 3.08 axles and 700R4 trans get around 23 MPG. Driving them here in the mountains of New York, some highway with many grades, and short trips - the fuel mileage is the same for any of them. The TH400 rig drives pretty steady at 65 MPH, although revving pretty high. The Blazers with 700R4s work hard on every uphill grade and shift in and out of OD, at 65 MPH.
Same story with my Suburbans. I've got 1/2 and 3/4 ton, TH400s and 700R4s, some with 3.73 axles and some with 3.42s.
I'll say this, though. I travel trough the UP of Michigan every year where the speed limit is 75 and most traffic is doing 85 MPH. I will NEVER drive a non-OD 6.2 diesel with 3.73 axles there again. 75 just barely feels safe, and 85 feels like the engine is going to blow.



Use a manual transmission instead of an automatic, and you can set it up for maximum mileage. Use a manual, and you don`t have problems with overheating, cooling and wiring. Use a manual, and you can tow in the highest gear (for maximum mileage). And you don`t have to worry about the transmission.


That "blanket" statement does not work. Many 6.2s when worked hard have cooling problems, regardless if hooked to an automatic or standard. And, as far as manuals never causing worry? What specific manuals? Many are crap and just as trouble-prone as lighter duty automatics, e.g. the TH350 or 700R4. Many manuals are weak, especially in 5th overdrive, as well as being weak in hard pulling in all gears but 4th - because of the load of the input shaft against the bearing in the output shaft. In 4th, the two shafts are locked into direct-drive and it's not a worry. Then there are other assoiciated problems involving clutches and pressure plates.
I've been a HD mechanic since the 1960s and had to replace and/or repair, many, many manual transmission parts and clutches. I also owned and beat on many a muscle car in 60s and 70s. Although automatics were not popular for street rods, those that were aound - with Chrysler Torqueflites, or GM TH400s - usually held up much better than the cars with manual trans. e.g. the Borg Warners, Saginaws, Muncie M21s, Ford top-loaders, etc. I still have my 65 SS Chevelle. After putting countless replacement Muncie M21s into it over the years, I finally changed it over to the TH400 and it's never bothered since. GM created the TH400 originally for use in the Buick Rivieria with over 400 cubes (401 or 425). It was bullet-proof, even the first ones that had two-stage twin-turbine torque converters.

Seems people here seem to refer to manuals as only the HD units - and then compare to the LD autos - which is silly. A TH400 can outlast many a standard trans and clutch setup - especially if the standard is an NV3500 5 speed or a NP833 four speed with OD. Now, compare a TH400 to a NV4500, or a Gertrag, and things change a bit. I have a Gertrag 5 speed in my Dodge Cummins truck and love the trans - but the original clutch setup is crap.

Even small low-power diesels can have their share of problems with standard transmissions. Look up the repair history on Isuzu P'UP diesel pickup trucks with five-speed OD manual transmissions. They were absolute crap, and rarely lasted longer then 60,000 miles. And, even my wife's Volkswagen Jetta diesels - we have two and each has a bad 2nd gear synchro. GMs with NV3500s rarely last past 100K miles if used for anything that resembles work, and the GM 833 four-speeds with ODs rarely lasted past 60K if used hard. My TH400 in my Suburban tow-rig went 420,000 miles before the first tear-down.

I think how the manual trans is used plays a big part.
i used to own an f-150 (95') with a five speed and a straight six.i believe the trans was a japanese job (mazda?)...i can't recall.anyway,my neighbor at the time had a similar setup,also a 95' with a six,and went through 2 clutches and a trans rebuild in a year,and i put over 135,000 trouble free km's on mine with the original clutch.he was convinced that the trans was crap.

i never should have sold mine.i loved that six.a great combo with the overdrive.

i think that an owner that grew up with manuals knows a great deal better when,how hard,and where to push things.especially off road or towing.far to many drivers seem to have learned with auto's...to the detriment of manual transmissions everywhere.

sadly,too many manufacturers install manuals that are a tad light behind engines that are a little large.to many engineers seemed to have grown up with auto's...:rolleyes:

I think how the manual trans is used plays a big part.


Well yeah, and the same can be said for automatics. If any setup is poorly designed, or power mismatched - then it's going to fail, regardless. But, a good setup, manual or automatic, if well cared for can last a long time.

My father-in-law has a 94 Ford F150 4WD truck with the 300 straight-six and E40D auto-trans. Plows snow all winter with it besides regular summer driving. Has 120,000 miles on it and has had zero trans. problems.

In regard to the GM 700R4s? I've got three, 1991 4WD 1/2 ton Suburbans - all with 3.42 axles, 6.2 diesels, and 700R4 transmissions. All are ex-school busses. All have between 110,000 and 140,000 miles on them - and I have all service records since new - and none have ever had any transmission repairs - and all three still work fine. In fact, I just sent in a sealed bid on a fourth - another 1991 with 130K miles on it along with a snow-plow.

Well, it`s just my experience: never trouble with manuals (not even a clutch replaced), always trouble with autos; a manual never makes me worry, an auto worries me all the time. Of course, all of them can fail sooner or later.

So next time my transmission fails, what do I do? Go back to a TH400? Try to put in a manual?

I think you guys are making an issue out of nothing. Comparing autos to manuals doesn't work. You can compare ratings and swap stories none of us have any way of verifying all day long but it doesn't do any good. Pick what you want. Want a manual? Get a manual. Want an auto? Get an auto...

Selecting a transmission is a very simple process. What you get is really determined by how much work you want to do during the installation and how much you want to spend on a tranny. The best transmissions for this application are probably the NV4500 five speed manual (OD) and the 4L80E four speed auto (OD). Both transmissions are pretty expensive and both require some modification to install (especially the 4L80E). They are probably the best combinations of strength and driveability, though.

Other transmissions are available for less money but you really get what you pay for:

The SM465 and TH400 are strong but they lack an overdrive. These are both inexpensive but durable transmissions that will serve you well but unless you have high rear gears or large tires you won't want to go on the freeway.

The NV3500, 700R4, and NP833 have overdrive but are weaker than the other transmissions. These are somewhat more expensive than the SM465 and TH400 but not as expensive as the NV4500 or 4L80E. All are decent transmissions that will serve you pretty well as long as you don't beat on them. All are relatively easy to install.

My personal opinion is that the 700R4 is the shortest lived of them all. Sure, plenty of them make it to 150K miles. That's generally about it though... Many of the lower $$$ rebuilds barely make it to 60K.

For me overdrive is a requirement. For anybody considering going with a TH400 or SM465 instead of a 700R4 or NV3500 or NP833 for durability that thinks they won't miss the overdrive try this... Lock your 700R4 in "D" instead of "OD" or don't shift to high gear on the manual. Now try and run the truck up to 70 or 80... I don't know what will happen with you but the fastest I can bear to take mine like that for any length of time is probably about 65. Now drive it without using the OD for a tank of fuel and compare your gas mileage. I think you will find in most cases that the overdrive is definitely worth having.

Want a manual? Get a manual. Want an auto? Get an auto...


Yeah, I tried to get a manual. The problem is that like 99.99% are automatics. And how many Suburbans did they build with manual transmissions?

Try to find either a van, a pickup or something like a Tahoe or a Suburban with a manual transmission, a Diesel engine preferably without emissisons stuff and without electronics, with four wheel drive and straight axles front and rear, for sale at a good price within 250 miles from here. Do think that`s even possible?



For me overdrive is a requirement.


Yeah, more or less the same for me. I need to be able to reasonably flow with the traffic at highway speeds. Though that`s possible without an overdrive, it wears out the engine, and it`s loud.

So what would one have to pay for a NV3500, NV4500 picked up on a junkyard?

I need to be able to reasonably flow with the traffic at highway speeds. Though that`s possible without an overdrive, it wears out the engine, and it`s loud.

So what would one have to pay for a NV3500, NV4500 picked up on a junkyard?

You can cruise all day long at 75- 80 MPH with 3.08 axles and no overdrive. I've got several with TH400s. And, using this setup does not wear the engine prematurely. The engine spins faster but does not have to work as hard - especially if you have a lot of hills. My 87 Suburban with a TH400 and 3.73s got 520,000 miles before the engine blew and it had a lot of tow miles at 75 MPH. It was pretty noisy though at that speed. I don't call 520K early wear.

In regard to pricing - the standard NV3500s are cheap - I've often come across them for $100 or less with private sales. In fact, I've junked a few S10 Chevys and with the NV3500s still in them. Prof junkyards though often ask $600 or more. They were designed originally, only to be used with engines 5 liters or smaller but the application got stretched to anything with a max GVWR of 7200 lbs, a max GCVWR or 11,000 lbs., or a engine with a max torque of 300 lb. ft. The NP833 four-speed manual with OD is rated about the same was OEM with many 6.2 diesels.

NV4500s cost a lot, often $1000 - $1500 used unless you get real lucky. They are also over 20" long.

The strongest and cheapest way to go - if you get lucky finding the parts cheap enough - is a SM465 with a Ranger "gear-splitter" put in front of it. That combo is much cheaper than converting to a NV4500, and stronger.

Go to http://car-part.com and you can check used transmission prices all over the country.

My 87 Suburban with a TH400 and 3.73s got 520,000 miles before the engine blew and it had a lot of tow miles at 75 MPH. It was pretty noisy though at that speed. I don't call 520K early wear.


Yeah, that`s not early wear. I`ve got 3.73s, too, and flowmaster mufflers. It`s much more quiet in OD, that helps a lot when driving long distances.


In regard to pricing - the standard NV3500s are cheap - I've often come across them for $100 or less with private sales.

The NP833 four-speed manual with OD is rated about the same was OEM with many 6.2 diesels.

The strongest and cheapest way to go - if you get lucky finding the parts cheap enough - is a SM465 with a Ranger "gear-splitter" put in front of it. That combo is much cheaper than converting to a NV4500, and stronger.


Hm, these are interesting options. I`ll read more about this.


Go to http://car-part.com and you can check used transmission prices all over the country.


ok :)

You can cruise all day long at 75- 80 MPH with 3.08 axles and no overdrive. I've got several with TH400s. And, using this setup does not wear the engine prematurely. The engine spins faster but does not have to work as hard - especially if you have a lot of hills. My 87 Suburban with a TH400 and 3.73s got 520,000 miles before the engine blew and it had a lot of tow miles at 75 MPH. It was pretty noisy though at that speed. I don't call 520K early wear.






You can but your head will be pounding. Even in my van, with a quiet muffler, towing in 3rd, the engine is screaming and after 20 mins, my head is also screaming, :(

I'm gonna be throwing a 6.2 in my '77 K20 with sm465 and 4.10s. I do have 33"s on it but, sounds like 55-60 is all I'm gonna want to push it to? Can anyone tell me how much faster I could go if I step up to 35"s??

I've seen somewhere that 6.2 with sm465 and 3.73s with 35" tires is a great combo. Anyone running this set up?

Sounds like any way I slice it 3.73s are in my future, although the truck rarely ever sees anything more then a 2 lane road with a 55 mph speed limit.

Here in oklahoma the average speed limit is 75mph. 85 on the turnpike. Im able to do this all day long with 36s and 4.56 gears. Me personally, i dont believe in tall gears or changing my tranny just to get an od. Just get taller tires.i tow a 5,000lb trailer with a turbo 400 daily, ive never had a problem with it. Reg. Maintenance and an oversize cooler.

Here in oklahoma the average speed limit is 75mph. 85 on the turnpike. Im able to do this all day long with 36s and 4.56 gears. Me personally, i dont believe in tall gears or changing my tranny just to get an od. Just get taller tires.i tow a 5,000lb trailer with a turbo 400 daily, ive never had a problem with it. Reg. Maintenance and an oversize cooler.

Any idea what kind of rpm your running with that combo at those speeds? Based on what your saying I should be good running 4.10s with 33"s on our 65 mph speed limit highways?

I'm gonna be throwing a 6.2 in my '77 K20 with sm465 and 4.10s. I do have 33"s on it but, sounds like 55-60 is all I'm gonna want to push it to? Can anyone tell me how much faster I could go if I step up to 35"s??

I've seen somewhere that 6.2 with sm465 and 3.73s with 35" tires is a great combo. Anyone running this set up?

Sounds like any way I slice it 3.73s are in my future, although the truck rarely ever sees anything more then a 2 lane road with a 55 mph speed limit.

35 inchers and 4.10 axles puts you at 2600 RPM at 65 MPH - which is liveable - but noisy. I've had to take my truck on a few trips with 4.10s, automatic with no ovedrive and 75 MPH - with stock 16" tires (31.5") and I was able to do it, but it wasn't fun. A stock 6.2 is governed to do 80 MPH tops - with 4.10 axles, stock 16' tires, and no overdrive.

35 inchers and 4.10 axles puts you at 2600 RPM at 65 MPH - which is liveable - but noisy. I've had to take my truck on a few trips with 4.10s, automatic with no ovedrive and 75 MPH - with stock 16" tires (31.5") and I was able to do it, but it wasn't fun. A stock 6.2 is governed to do 80 MPH tops - with 4.10 axles, stock 16' tires, and no overdrive.

So I'll be pushing it running 65 w/ my 33"s?? Think I spin about 2400 or so at 55 right now with my 355.

Dont know my rpm's, no tach. I do know that at 90mph, im topped out. Not so much noise though, i hear my tires much more than my engine. Maybe im just numb to it (to much skynard ha ha!!)

Dont know my rpm's, no tach. I do know that at 90mph, im topped out. Not so much noise though, i hear my tires much more than my engine. Maybe im just numb to it (to much skynard ha ha!!)

Kinda off topic but you mention no tach. I didn't even think of a tach on a diesel, where does one hook up without a distributor??

A bit OT too, but since you´re discussing automatics....My Jimmy w/ a TH700 drops down from OD to third at the slightest incline, unless I´m driving over 60mph. Oil level is OK. I wonder if the kickdown-cable is adjustable? Could that cause the downshifting?

Edit: The alternator needs to have a W terminal to hook up a tach.

A bit OT too, but since you´re discussing automatics....My Jimmy w/ a TH700 drops down from OD to third at the slightest incline, unless I´m driving over 60mph. Oil level is OK. I wonder if the kickdown-cable is adjustable? Could that cause the downshifting?

Edit: The alternator needs to have a W terminal to hook up a tach.

You don't have to have the W terminal - you can install a stator-tap on any alternator. Having the W terminal - like Volkswagens use, does make things a bit easier.

In regard to your 700R4 shifting in and out of OD on the highway - all of mine have done that since new with 3.08s axles - especially with oversize tires. 6.2 does not have enough power to sustain with 3.08s in OD. My trucks with 3.42s - or 3.73s - don't do it. I put a shut-off switch on mine and leave the lockup converter turned off - unless I'm on a flat highway. Runs much nicer that way - the torque-converter slippage is just enough to keep it from shifing back and forth.