How many miles will these tranny's go for with normal use?

If you keep fresh fluid in it, change filter often, don't tow in OD, don't brake torque it, they can last a long time. Seen 'em well into the 200,000 mile range with only fluid changes.

153000 kms. not miles kilometers is what mine got. i bought it at 124000

don't tow in OD,

Are we dealing with a truck with a manual boost control? Benny -Are you aware that stock programming limits boost if not in OD! Rolled over the scale today at 24,000 gross and I towed that into town in OD - in fact I have been towing into town with scrap at 21 - 22K GVW for the last few weeks, in OD. Sure Benny Ill give you some slack re: you need to tow in a lower gear IF the EGT's are climbing over 1000 degrees and your still scrubbing off speed and RPM, or your load and speed forces the converter to go in and out of lock up. – Can’t have that now can we? You need to watch your Trans temp too.
But - Making a blanket statement like that is unnecessary at best. Some one recently posted about the credibility of the advice we may be receiving.....I wonder!
Oh and I am a "parts man" - What are you calling me in your sig?????
My Name is RICK!:rant:

So another words if you're shifting in and out of overdrive drop it a gear but if your not leave it in overdrive. I don't know about that. There's been guys with 454's pulling in overdrive and in about 50 miles there tranny's went out. I worked with a guy who hauled scrap and he had a 96 1 ton with a 454 and he never pulled in overdrive not even with his trailer empty.

Stingthieves, I'm a parts guy, too. My old boss had that saying on the wall, always thought it funny, no offense intended.
Not towing in OD is straight from the owners manual, reasoning is that in 3rd gear, engine RPM is higher, thus trans fluid pressure is higher, keeping more pressure on clutches. In fact, my Sub has a sticker on the driver door jamb stating just that also. The few 4L80E's I've seen burnt up all had the 4th gear clutches fried from towing in OD. I didn't see the owners drive, I'm sure many tow in OD with no problems, I just go by the book.
I was not aware that PCM adjusted boost dependent on selected gear, does that apply to all years or a specific range?
When I moved from MI to TN, I kept it in 3rd the whole time, yes, poor mileage, but plenty of power, had a 28ft trailer with about 6000lbs of my crap inside.

Correct me if I'm wrong but if you are towing in OD and and temps stay within the normal operating range what's the harm? Heat, I was lead to believe, is the destroyer of a transmission. I tow my 5'er in OD until it begins to hunt and then will down shift to 3rd. I also run with synthetic fluid and an additional cooler. Sticker on my door jam also says not to tow in OD however, a lot of discussion on this subject in RV.net and the consensus is most tow in OD while on the flats and down shift when you get to the hills.

360 000 kms and still going on a 97 6.5 TD......95% highway kms though (unloaded)....

I tow in overdrive all the time. No problems. The money I save on fuel and engine wear by running in overdrive will out weigh the costs of rebuilding my transmission a year sooner than towing in direct.

So another words if you're shifting in and out of overdrive drop it a gear but if your not leave it in overdrive.

If the converter is "unlocking" - drop a gear - in and out of lockup will build heat really fast - yes its heat that kills - I monitor my trans pan temp and it stays 150 maybe 160 if im am working it - but working it means I am lifting my foot because of EGT's and I change my pan fluid and filter once a year just because - the fluid is still nice and bright red!

I don't know about that. There's been guys with 454's pulling in overdrive and in about 50 miles there tranny's went out. I worked with a guy who hauled scrap and he had a 96 1 ton with a 454 and he never pulled in overdrive not even with his trailer empty.

A guy with a 454 and no regard for his equipment can kill anything! Please don't compare apples and oranges. Watch your gauges. I have a long low grade pull from a stop sign and Ill start out selecting 3, watching my EGT holding about 900 degrees. If I started in OD I would lock up too soon! Whatever speed I make - that’s what I am making - ill switch on my 4ways if I have to – pass me! But when I make 50mph and my boost just begins to fall - Ill lift my foot and bump up into OD, let it lock up and get back on - if I have read the grade right – my RPM is now about 1800 my EGT falls off 100 degrees, I gain 5mph hold that - with continued egt drop till the next grade. If I can hold 1800 RPM and 900 EGT – I hold it. If not [ egt goes up / RPM has come down to 15-1600] – I lift and drop to 3 - Or I could continue to crank along just over the power / economy band of a 6.5 at 2500 - 2700 rpm and just listen to the radio. But its all good right? What ever works and keeps these old girls running – that’s the challenge. Anybody can go spend a Jillion Dollars for a new truck with other issues!
Kind Regards
Rick

I have 120,000 on my truck now with only fluid and filter changes to the trans. I do commercial plowing all winter, a few sled pulls every year, my share of burn outs and towing. Fluid changing is key to long life

I've got over 225K km on my 96. It's towed all over the place, always in OD, and in the winter it pushes snow.
Fresh fluid and filter yearly and a flush now and then keeps it working fine.

IMO, a 4l80 will work well until you get way the hell in the middle of nowhere, and then take a crap. I'll never own another one

My 94 has 398000 km on it.It has been drivin by every throttle jockey coming down the pike.
It has been a Escort Truck since 2000 when we got it.Fluid changes every 6 months on the tranny has worked well.
Too bad some of my ex drivers didn`t work that well or long.

I forgot to add I always tow in OD.

Can only pass on my own experience. I used my 95 for only towing my 5er. 8000 lbs on the scale. I have heavier cooler than factory, deep B&M Tranny pan and trans tem guage. I have never had a problem towing in OD which I do alot. That said, I watch temp very close and also pay attention if tranny wants to hunt. I also believe that maintenance is a major factor. Since I tow only with the truck I change filter once a year and fluid twice unless I put on unusually more miles then I will change filter twice. Never had a problem in 89,000 miles of towing. You can quickly ruin any transmission if you don't use common sense.

I've got 160K with great maintenance. Clean fluid and don't over heat. I've got about 30 or 40 of these in every configuration at work. Some are 11 years old and the trans. are original. Fleet drivers are hard.

I see that pulling with a 6.5 is a little different than pulling with a 454. The guy i mentioned earlier got 220000 miles out of is tranny before it went. he changed tranny fluid and filter every 30,000 miles. he mantained everything on his truck very well. I heard now he bought a 2003 1 ton duramax. I wonder how that's working for him? He still has is old one for short trips picking up scrap around farms and buisnesses he picks up at. Sounds like with a 6.5 you must have gauges

With any truck you are using to haul, if you want it to live you should have gauges, and for pete sake pay attention to them!:lol:

The most succesful way to damage this trans has already been discussed previosly in this thread. Hunting between 3rd & 4th is damaging enough but towing with convertor unlocked creates more heat than anything in any auto trans. If you get fluid hot lubrication suffers. Heat makes the non multigrade fluid thinner & line pressure suffers & aireation occurs this definately causes 4th to get burned especially when the trans is hunting. Because 4th is coming on & off with thin, overheated, aireated, low application pressure fluid.

My 4L80E failed after a trip to DC trough the West Virginia mountains where I failed to shift into 3rd after it kept hunting between 3rd and OD. Even then it failed after I got back. The rebuilder said an actual gear was fractured, but the clutches were in good shape. On the way home I towed in 3rd and the performance was a lot better.

how do u take it out of overdrive.. I dont have a switch in my 98 gmc??

Put the shift lever in D instead of OD...

Towing in OD is fine...AS LONG AS THE TRANNY ISN'T CONSTANTLY DOWNSHIFTING...where people run into trouble is the tranny constantly kicking in and out of OD, creating excessive HEAT. If you're a flatlander, or towing something small and light, you shouldn't have any problems...in the mountains, and even in the foothills, you need to be more careful and pay attention to the shifting characteristics while towing.

More impotantly than keeping it in OD id that the lockup convertor stays locked up in OD. More heat is made by torque convertor than anything else in trans. If in 4th & not locked up all the convertor slippage creates great amounts of heat. If this is the case you're better off in 3rd with engine RPM higher which creates less convertor slippage even if it is unlocked, & you have a better chance of keeping convertor locked up & creating alot less heat. If the load is light enough to pull 4th gear & keep convertor locked up, you can leave it in 4th. (IF pulling a hill or warm climate & engine temp crawls a little too high you can also drop to 3rd which will speed Water pump & fan for more cooling.)

My engine runs alot hotter in Drive than in Overdrive when towing.

Keep filters changed, fluid fresh, should do fine, heat is what kills these trans,

If towing heavy, deep pan, extra cooler, tow valve body, and gauge, (all things THE typical shade tree mech can do) so far so good on mine even on hotest of days towing that backhoe shown in my garage, most times I'm in OD, max pan temp runs no more than 200F.

My engine runs alot hotter in Drive than in Overdrive when towing.

Ditto for me on this. Towing approx. 6k pounds.