4L80E running hot

[rcull]

When pulling a heavy load my transmission is getting way too hot too fast. Could I have a problem with torque converter lock up?

Am I right in thinking the only thing that should be building much heat is the torque converter?

Thanks

[Yukon6.2]

Hi
When was the tranny serviced last?
Have you ever cleaned between the rad/ac/tranny coolers?
And last does the oil look dark,or smell burnt?
And if you add more details,year/mileage/yrs owned ,any history may help with advice on things to do.
Good Luck
Thomas

[rcull]

It is in a '96 3500. Yes, I have cleaned the radiators. I have also taken out the small one that is on the '96 and put in a larger engine oil cooler like on the '94. I have had the truck for some time, maybe 8+ years. It has always had a transmission problem.

Story or whooes...

I bought it, it had a new GM transmission in it along with a fancy oil cooler. We were going up a wintery hill and a poorly installed cooler line blew off. We didn't recognize the problem 'till it was too late. 2nd rebuild. Then I had to pull a heavy load up 15-20 miles of logging road. There was an electronic failure that caused the next problem. Third transmission... I now notice high tempreture when pulling, maybe too high anyway. Yes, after today, I could smell the oil when I got out of the truck. I would be surprised if it wasn't burnt.

Thanks for your input

[rustyk]

I had a similiar problem, which was traced to a failed TC (not just lockup - which is going to unlock under heavy load, anyway). I had the tranny rebuilt by Suncoast Converters, and also got its brazed TC and machined spline. Tranny runs now at around 145°F. When the problem arose, it would be up to 180° within a few miles, also spiking the engine coolant temps (tranny cooler is integral with radiator).

[greatwhite]

With that many rebuilds under it's belt, I wouldn't be surprised if there's some used plates and friction disc's in there.

Could be some slippage which can cause excess heat.

There could also be wear int he valve body assembly effecting line pressure and also leading to slippage.

Are there any fault codes stored in the PCM related to transmission faults?

[DmaxMaverick]

Heat caused by clutch disc slippage is temporary, and usually goes unnoticed until the tranny is toast. Any significant disc slippage will cause ratio faults, and corresponding DTC's. The suspected TCC delay or dysfunction is probably the right direction.