96 Suburban 2500 4x2 Transmission Question

[torque454]

I may be buying a 96 3/4 ton suburban, 2 wheel drive with a 6.5 diesel. It has 225,000 miles on it. The transmission has never been rebuilt. It doesnt seem to give any problems, not when cold, or hot or anything. The torque converter locks and unlocks when it should. The only time i the truck does anything strange at all is when im pulling a hill, and i have to make the truck work, like, when it comes out of overdrive and my foot is on the floor, it jerks once in a while, say maybe every 10 seconds or so. Once it goes back into overdrive and im no longer working the truck to pull the hill or whatever, it doesnt do it anymore. I dont know if its transmission related or engine but thats the only strange thing i could think of that it does. Now then, the truck belongs to my boss, and id be using it to go to work, including pulling my 7,000 pound power washer trailer when i am not busy with him. He says the only reason he hasnt sold me the truck yet is because he is worried that he'd sell it to me and then something would go wrong with it. Now with that being said, ive driven the truck myself for the last 2 1/2 months and there is nothing seriously wrong with it. Nothing i am concerned with *except* the transmission. Even then that is only because of the milage on it. It doesnt give any indication whatsoever that there might be any problems with it, unless that jerk i described is the transmission. It doesnt leak and the only noise it makes is in first gear around take off, it sounds just like any other heavy duty transmission ive heard, like in a school bus or something. That whiney noise they make as they speed up. It doesnt shift oddly, ever. Not when cold, not when hot, or any other time. It just has 225k on it, and has pulled, alot. Now the question is, how long does a 4l80E transmission typically last if taken care of? Boss has never abused this truck. Its never been run hot, always had its maintainence. He doesnt try and race people to the stoplight or drive like a bat out of hell. His driving habbits are closer to those of grandma and grandpa. Does it sound like i should really worry about it, or should i just find another truck thats maybe had transmission work done less that 225,000 miles ago? lol.

[grancito]

The jerking on high fuel demand is more likely to be lift pump problem or dirty fuel filter. Autos don't have a square cut low gear like a bus and therefore should be quiet.

[torque454]

The lift pump is new but not sure about the fuel filter. Probably need to drain the stuff out of the fuel filter bowl, too. School buses dont use the same transmissions that heavy duty pickups use?

[grancito]

No, the general public won't accept the noise, in modern cars/pickups. The gears are "helical cut to be noise free, and they are planetary gears in auto trans, even more quiet. I have a 3/4 ton with 4L80E and it is quiet.

[torque454]

Hmmm well dont know whats going on then. If i take it to a transmission shop can they run a test on it or something and tell me the condition of the transmission?

[grancito]

If they drive it and it sounds like an old school bus in first gear they will want to rebuild it. It most likely has worn bearings in the planetary gears so that they don't mesh right and hence make a noise, or the bearings are making the noise.

[torque454]

If they drive it and it sounds like an old school bus in first gear they will want to rebuild it. It most likely has worn bearings in the planetary gears so that they don't mesh right and hence make a noise, or the bearings are making the noise.

Not what i wanted to hear :( lol. Think it would make it pulling 7,000 pounds for a while? I just need it to last long enough to get my business started and making a decent income. If the trans goes down hill then, id be able to afford a rebuild. Im afraid of the bill tho. That could be probably $3,000. The whole truck probably isnt worth much more than that, but if i put that in it and get 200k more out of it (shouldnt be too hard to do with a diesel) it would be worth it.

[grancito]

Could be that it had to pull hard in low gear a lot so it wore. If you did not tow with it and was easy on first gear, it could last some time. One of the costs of a repair is that the shop doesn't want returns so replaces everything. I rebuilt the 700R4 in the Chev last time, it destroyed the first/ reverse roller clutch and I had both first and second gear at the same time. Makes a good parking brake. On dissasembly, it had 170,000 miles since last rebuild, there were no worn parts, just the broken pieces, cost $35 to repair. If you could find someone to make a repair like that without guarantie you could still get a lot of miles out of the transmission for little cost.

[torque454]

Well the truck is titled as a 1/2 ton, was ordered a 1/2 ton but is labeled 3/4 ton and has 8 lug wheels. However i beleive it has 3.42 gears which the way i undestand it are only supposed to be 1/2 ton gears. So, with that being said, the 3.42 gears will be harder on the transmission than the 3.73s or 4.10s especially in 1st gear. So 1st gear probably did get alot of hard use. I like the 3.42s because of the milage they give me. I'll look for a shop that will just fix whats wrong if there are any out there. That is, once it starts giving problems.

[grancito]

That all sounds logical except the weight confussion, wonder how that happened?

[Chevylover]

Use the search function on the forum ! Some weeks ago, there was a thread where somebody got the same problem. Suburban 1500 but with 8-lugs and so on. Another meber told us, that all 6,5 TD Suburban are delivered with 8-lugs and 3,73 gears, including the 1500.

Cu,
Sven

[torque454]

Use the search function on the forum ! Some weeks ago, there was a thread where somebody got the same problem. Suburban 1500 but with 8-lugs and so on. Another meber told us, that all 6,5 TD Suburban are delivered with 8-lugs and 3,73 gears, including the 1500.

Cu,
Sven

This one has 3.42s, im about 99% sure. I know its positrac and that the gears havnt been changed. My boss has owned it since it was new and says its had no work like that done. He did say he ordered it a 1/2 ton tho and when he got it and saw the 2500 emblems and the 8 lug wheels, he made them start checking things to see if it really was a 1/2 ton or not. He said the guys told him the springs had the part number of a 1/2 ton, tho ive always understood the same springs were used between 1/2 and 3/4 tons, just some have more leafs than others. This ones got alot of leafs. I havnt counted them but i know its alot and theyre thick. Im betting its a 3/4 ton frame, axle, and brakes, but with 1/2 ton (3.42) gears and maybe springs (if they are indeed different). Still basically a 3/4 ton.... I cant imagine them putting 8 lug wheels on a 1/2 ton. Ford puts 7 lug wheels (yes i meant 7) on their heavy halfs today. (thats what boss replaced this truck with) 7 lugs. Thats stronger than standard 1/2 ton truck, but weaker than the 3/4 ton.

[grancito]

Look for the option codes in the glove compartment, the ones begining "G" will tell you the axle options. You can find them on the internet under GM option codes, or I'll load the disc and tell you.

[sixfivekid]

if your saying it only jerks when ur making it work on hills it could be that your torque converter is slipping

[JD_countryboy]

I had what was diagnosed as a bad torque conveter. It didnt jerk, but you could hear it it "chatter" upon torque converter lockup at any temp. once tranny got warm, torque converter would unlock toatly and sometimes downshift. Of course I went thru my tranny and rebuilt it since it was out to replace torque converter. problem solved.
I have seen once what was supposed to be a 1/2 ton with a 6.5 td with 8 lug wheels and heavier springs. I was told that with the diesel engine option they came with a heavier suspension to hold up to the diesel power.

[torque454]

if your saying it only jerks when ur making it work on hills it could be that your torque converter is slipping

The RPM's dont seem to change when it does it tho. It is possible tho i guess.

[sixfivekid]

my dad has a cummins with an automatic in it. we have a 5th wheel camper and a gooseneck horse trailer and on bigger hills it would slip causing the jerk you were describing.

[grancito]

I had a torque convertor fail, it shuddered and slipped in lock up before the internals disintegrated. I think the hickup is fuel related. Easy check.

[torque454]

I dont think its the transmission or torque converter, because if it was it would do it worse and more frequently while pulling a trailer. It doesnt. Now if its fuel related, it could be slightly worse, because a diesels fuel increase under load isnt all that much. (unlike a gasser)

[grancito]

Sure it increases under load, basic physics, there is no free energy. Make it work twice as hard, it requires twice as much fuel.

[torque454]

Yes, but since it doesnt consume as much fuel as a gas engine does to begin with, its increase in consumption is relativly small. Gas engines seem to eat fuel 10x as bad under load (least all my POS gassers have).

[962500]

my truck is a 96 2500 2wd and it has 425000 km on the clock and it has the same problem. when i put my foot right to the floor even when its not loaded it will surge or jump like that. i have always figured it was the transmission but the lift pump could be the problem. i talked to a transmission guy and he said that if it starts to jump just push your brake pedal down just a little bit and if it stops its the torque converter because the brake switch should unlock the converter when the pedal is pressed. i just havn't had the chance to see if that is the problem because the truck hasn't done it since then.

[torque454]

my truck is a 96 2500 2wd and it has 425000 km on the clock and it has the same problem. when i put my foot right to the floor even when its not loaded it will surge or jump like that. i have always figured it was the transmission but the lift pump could be the problem. i talked to a transmission guy and he said that if it starts to jump just push your brake pedal down just a little bit and if it stops its the torque converter because the brake switch should unlock the converter when the pedal is pressed. i just havn't had the chance to see if that is the problem because the truck hasn't done it since then.

Yea the brake pedal unlocks the converter but with the accelerator pedal to the floor the the trans should have the converter unlocked and be in 3rd gear anyways. The lift pump is new on my 96. It may need a fuel filter.