Overdrive problems. Please help!

[k2500burb]

Ok I have a 1996 k2500 gmc suburban 4x4 with the 350 and a 4l80e. my problem is when im driving down the road in overdrive, once i get up to about 40 mph or greater, something slips and the engine revs up and rpms rise as well. Its almost like its going into passing gear but its just not actually accelerating. If i put it in 3rd then it runs like normal. Has anybody had this problem? Thanks.

 

[k2500burb]

bump..

 

[MikeRWK]

Sounds like a burnt band

 

[Chris]

A 4L80 only has a reverse/overrun band. All shifting is done via clutch engagement unlike a 4L60. Check the fluid level/condition first, and if it passes muster then most likely the OD clutches are gone. Commons problem with high mileage 4L80s.

 

[k2500burb]

Fluid is good. I check it often. I stopped by a transmission shop and one of the mechanics seems to think my torque converter is taking a **** on me.

 

[k2500burb]

It was rebuilt around 160,000 and im about to hit 180,000.

 

[Chris]

Doubt it. Doesn't sound like a TCC lockup issue. Put it in "3" on the column, and get up to 55mph steady. While holding that speed LIGHTLY put your foot on the brake and see if the rpm climbs on the tach. It should drop once you release the brake. Quick and easy way to check TCC function. Definitely sounds like the OD clutches are on their way out.

 

[k2500burb]

Ill give that a try when I get home. Thanks man.