I have an 87 3/4 ton with 6.2 and a creeper 4 speed. I love it until I want to go over 55 mph.

I take off in 2nd, i'm in 4th by 30 mph and can't go over 60. I have read here that a 700r will suck all of my power (I pull trailer quite often) but I have to make this thing go faster on the highway.
BTW I have 4:11 rears.

I would like some advise, are there different manual trannys that I should consider, or will a swap to an overdrive auto be the answer.

how about a 5spd std out of a later gm truck looks almost the same as your old 3 spd with the granny gear

I would like some more information, it it is a bolt in, I would go that way.

I forgot to mention that my truck is 4x4. I am going to need some specifics as to what to look for, and what is actually interchangeable.

I'm guessing the best solution is to call a tranny shop.

rpratt, the 4.11 is what is holding your speed down. An overdrive trannie would help but a 3.73 or 3.42 differental would do better. A taller rearend takes less power to pull than an overdriven trannie. If you use an automatic towing in overdrive can bring you greif. With taller rearend you could keep your grannie gear. Mike

That makes alot of sense, it isn't what I wanted to hear, but it is well thought out and correct.

Check out a U.S. Gear overdrive. I installed one in my dads old 6.2 suburban that we also swapped a 4 speed into. It is electric shift and allows splitting gears, on a 4x4 it goes between the trans and transfercase.;)

How about going up one or two tire sizes.On a 3/4 ton you should have good fender clearance for the fronts.

Sub5, that is a real good suggestion. Many years ago, on my 63 Chevy 3/4 ton, I swapped out 15.5 inch wheels for 17 inch split rims off a junked bread truck because it needed tires bad. They cleared ok, maybe because they were so much thinner than the 15.5s. Made that old gal a real cruiser. As I remember the 15.5 rims were on the truck when I bought it used. I am not sure if they were original equipment or not. It was a great truck but any thing over 55 MPH was winding that 250 pretty tight. The bigger wheels took care of that and it didn't hurt the power. A lot of people mistook it for a 4X4 because it sat so high. I really loved that truck. The 250 was shot so I installed a free used 283 (out of a demolition derby car that got creamed right out of the gate) with duel glass packs. You could hear it coming a mile off. Drove that old truck a ton of miles. Mike

Towing in o'drive is not a problem if you buy a "real" transmission. GM cheaps out, one of these babies is what you need. Check out http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33727&item=7968722524&rd=1, or http://www.transmissionhead.com/. These trannys had a crappy and well deserved reputation from day one (1991). Read, read, read, and buy, buy, buy!! 700R4 will drop your final drive 35%. IE; 4:10 is 2:90 or so. You can also specify a "higher" 1st gear. 700R4 has a grannyish gear, 2.76 instead of 2.48 of TH400. I will be installing one of these HD rebuilds with a full-time NP203 trans case. Transmissionhead sells an output shaft to mate the "new" trans to the "old" FT TC. A few parts from www.milemarker.com (http://www.milemarker.com/), and I'll be ready... for the doghouse :(

The newer 5-speeds have the slave cylinder low on the passenger side. Some people speak of driveshaft clearance issues. Since the light-duty version has an integrated bellhousing, that only leaves you with the NV4500. A/A makes a custom bellhousing, or you can swap in the longer Dodge input and use an adapter plate. Your t-case will bolt right up.

For the trans swap, you will likely have to budget for modding two driveshafts in the process.

IMO, the ratio swap is an easier solution. Get a complete rear end and time it together with a brake job. Then you can shop around for the matching ratio for the front, and swap it in later.

I'm looking at a Blazer that was wrecked, it has 1 ton axles and a lift kit, big tires, small block 388 that is really nice. I think I can part the blazer out and end up with a set of axles.
I'm gambling that I want to make changes to this truck and watch gas prices rise faster than Diesel.

Take your truck out of 4 wheel drive!!!! My one ton with a 6.2L and 4.56 rear end has no trouble in driving 80 MPH with my heavy camper, but I usually drive 60-65 MPH. And I have your same manual transmission.

There is absolutely NO WAY I can go 80 MPH..... maybe down hill with it out of gear, or with a tow strap hooked to YOUR truck, other than that, there is NO WAY!!!

FWIW, I swapped a 3.21 axle into my Burb. The 4.10 ratio was just too much for the highway (felt like I was killing it over 60mph). Since I have a TH400, the bottom end has suffered somwhat.

However, I think it will be just about perfect after I put in the SM465 and have that granny gear ):h

EDIT: Cougarjohn, elaborate on your rig please. 80mph & 4.56 ratio doesn't add up for me unless you have large tires, OD, or some significant engine work. :confused:

I found a link to installing an NV 4500 5 speed transmission in place of the creeper 4 speed.
It specifically has details on 6.2 conversion. I need to do some more homework on it, but this might be the way to go for me.

http://www.high-impact.net/transmission_and_gear/nv4500_gm82-93diesel.htm

I have installed nvg 4500's behind 6.2's, it's not hard, but it is expensive and you can't use Advanced Adapters bellhousing, it won't clear the starter on a 6.2. Just ask and I can give you the answers to your questions if this is the way you want to go. 65 mph with 235/85/r16 tires and 4.10's should be about 2800 rpms. A healthy 6.2 should rev to about 3600 rpms, or about 75 to 80 mph. If your fan clutch is not releasing the way it should it will keep your speed down due to the parasitic hp drain. If your truck won't rev to about 3600 rpms, your injector pump might have some problems. I used to check for soundness of injection pumps based on top speed. A weak pump will only let you run around 70, a healthy pump will run all the way up against the governor.:eek: :cool2:

I believe the truck would go faster, I never tried to go to the governor, but I feel confident it would do it. The fan does not disengage (most of the time) but has been the last couple days.

What brought me back to this thread tonight...... My granny gear tranny gave up the ghost tonight. I thought these things were bullit proof.

It popped in reverse, wouldn't go forward for a minute, then made a bunch of bad munching gears type noises.
It did get me home, but 2nd gear at idle, and it locked up the tires once about halfway home (2 mile drive).

I guess I'm doing something about it this week after all!

Ouch:( could be time for a tranny swap. Those sm465's are pretty tough, but everything can break.

Make sure your tranny is the problem and not the rear end:confused:

Make sure your tranny is the problem and not the rear end:confused:
I asked a freind to come over today (during daylight) to look at what is happening under there, I was concerned about the same thing.

u2slow: I have the 3 speed + granny gear trans, 4.56 rear end, and LT235/85R16 tires. I also have the speedometer converter on the transmission and my speed is accurate. I don't drive at a sustained 80 MPH, but I have sometimes in passing. My engine is a 1984 mfg., but it still puts out max horsepower and min. smoke on the county dynamoter.

Make sure your tranny is the problem and not the rear end:confused:
It didn't take long to find out it was the transfer case, it had a large hole in the front half of the case..... I'm sure you know right where the hole was, I read that it is a common failure spot.

I bought a 700R with another 208 for future swap but I also bought a new 208 to get me back on the road for now ( long story, didn't read enough).

I read somewhere that there is something that allows the 700 to shift without electronic signals, it is hydraulic, or fluid driven. Please advise.

[QUOTE=D.Camilleri]I have installed nvg 4500's behind 6.2's, it's not hard, but it is expensive and you can't use Advanced Adapters bellhousing, it won't clear the starter on a 6.2.

Actually, I just bought a Powermaster starter tonight for the 6.2 (Summit part # PWM 9052) and it's a gear reduction type starter with no nose cone. It does clear the Advance Adapters bellhousing and my assumption is that it should work just fine with the gas bellhousings too!

:cool2:

The 700 auto trans. is not a very good transmission. I have known several people that replaced them with the GM 400 series when their 700 units failed.

The 700 auto trans. is not the best trans. I would go with the GM 400 series before I installed a 700 unit. My preference would still be the 3 speed manual with granny. My only maintenance so far has been to replace one of the shifting forks plus the front and rear seals. I have about 225K miles on the unit.

I understand that there are horror stories about the 700 tranny, but I suspect that they fail most often in the trucks with 3:xx gears in them.

I have accumulated most of the parts to do the conversion to 700R, (tranny, T-case, TV cable) but I'm not ready to jump yet.

I am assuming that a 700 would be fine in a truck with 4:56 gears (or 4:11) but I do alot of towing a car trailer with the truck.

My only desire is to bring the RPMs down, and to move at a reasonable rate of speed on the highway for a reasonable amount of money. If I had a bunch of money, I would have bought a new truck and not thought about all of this for one second.

My '82 had the 700 and really didn't have many problems. You do need the proper torque converter. I can't remember how the shift control was different between a gas and diesel trans. I'd talk to a trans shop to determine the internal differences before making the swap.

I never had a problem with running higher rpm either. We run HUMVEE's hard on the highway with no problems.

sureCheck out a U.S. Gear overdrive. I installed one in my dads old 6.2 suburban that we also swapped a 4 speed into. It is electric shift and allows splitting gears, on a 4x4 it goes between the trans and transfercase.;)
are you sure they go between? I used to seel those and all the ones I put in went behind the t-case. there was a wiresetup that tied to the 4wd indicator to keep you from putting it in gear while in 4wd.
but there may be a modle that goes in between.
I recall them being very costly, reason quit selling them. half a dozen of them sitting here on the shelf at a time, tieing up money.

It didn't take long to find out it was the transfer case, it had a large hole in the front half of the case..... I'm sure you know right where the hole was, I read that it is a common failure spot.

I bought a 700R with another 208 for future swap but I also bought a new 208 to get me back on the road for now ( long story, didn't read enough).

I read somewhere that there is something that allows the 700 to shift without electronic signals, it is hydraulic, or fluid driven. Please advise.
yes, you can mod the 700 to do that.
it will shift fine without any electric signal, its the convertor that won;t work right, no lockup. most tranny guys will tell you, and some other 6.2/6.5 sites, that you cannot run one without the tcc solenoid hooked up. that is pure bull, I have run them for years and thousands of miles like that.
there are lots of variants fo the 700 wiring scheme. some lock the tcc in 2nd,3rd and OD, some in 3rd and OD only, some in od only. depends on how the internal pressure switches are wired.
if someone wants to keep electric control, i rewire them to only have tcc in OD.
but the best way is to get the hydraulic diesel converison or the tcc from your local transmission rebuilder supply house.
MY 84 4x4 under normal throttle will lock the tcc at about 40 or 45mph.
that changes with throttle pressure.
the mod makes the tcc look at throttle pressure, and governor (in the tranny, not IP)pressure.

What is the proper engine RPM when cruising at 50 mph? Here that is the top speed for my truck. Now it's a bit over 1200 on OD.

I have 14-bolt FF waiting for the swap (just need convert it to discs) and it has 3.73 gears. That brings RPM up to near 1500. Should I go on lower gears, or settle for 3.73?

The 700 has only a small 4-pin connector on the left side of the case to operate the lockup clutch. The sister 4L60 has a larger computer connector. It is electronically controlled by an ECM. It, too is convertible with proper parts. I would stay away from the 4L60 and go with a '87 and later 700R4 core. The '88-'91s have the auxillary valve body, making them a little more complicated to assemble. Other than that, all 700's are about the same.

The real trick is this trans has a long history of upgrades. There are seven different input shafts available depending on who you talk to. The '87 6.2 diesel 4X4 H.D. 3/4 ton core is my first choice for rebuilding. it has all the latest stuff and will work well. There are after-market parts to improve things even further. Cost is the only factor on how far to go. The diesel version has many more switches to control the operation of the TCC. Be informed before you swap as there are many pitfalls to making a 700R4 work well. A reputable trans shop can be a good source of info.

The 700 has only a small 4-pin connector on the left side of the case to operate the lockup clutch. The sister 4L60 has a larger computer connector. It is electronically controlled by an ECM. It, too is convertible with proper parts. I would stay away from the 4L60 and go with a '87 and later 700R4 core. The '88-'91s have the auxillary valve body, making them a little more complicated to assemble. Other than that, all 700's are about the same.

The real trick is this trans has a long history of upgrades. There are seven different input shafts available depending on who you talk to. The '87 6.2 diesel 4X4 H.D. 3/4 ton core is my first choice for rebuilding. it has all the latest stuff and will work well. There are after-market parts to improve things even further. Cost is the only factor on how far to go. The diesel version has many more switches to control the operation of the TCC. Be informed before you swap as there are many pitfalls to making a 700R4 work well. A reputable trans shop can be a good source of info.

Thank you for that sound advise Fred, I decided to keep it together the way it is until I am confident that I have everything figured out.

Send me a private message and I will give you some additional info on who and where to get parts and pieces for it when you decide to rebuild it. I have some internet sites with info also. Fred

rpratt, I just r&r ed a nvg 241 transfer case (very similar to a 208)out of an 89 suburban several days ago. The reason- oil leaking from transfer case, a crack to be exact in the area of the front out put shaft. I removed it and welded the crack, but my point is what I believe caused the crack. The grease was hard in the front drive shaft slip yoke and when I tried to compress it, the slip yoke hit a hard spot and wouldn't go. I worked it a bit and finally got the grease to squirt out of the relief hole and then the slip yoke worked propper. My point is, this was the reason for the case failing- the hammering of the slip yoke against the front output of the transfer case. Check your front drive line to make sure your slip yoke isn't bottoming out.

In regard to my other suggestion of the US Gear overdrive, they definetly go in between the transmission and transfer case and are very durable. The unit that goes behind the transfer case is a Gear Vendors unit, and like my mother used to tell me when I was young, If you don't have anything nice to say...............:cool: