In a 06' Buick Raineer with the 4.2L I-6 with 70k miles. Its only towed a 5x10 trailer with a 4wheeler on it 3 times and the rest is mostly highway miles. Well the SES light came on for trans slipping so I helped my cousin (owner of the Buick) change the fluid and filter. There was alot more copper than normal in the pan and the fluid was pretty burnt. After the fluid and filter change we ran 2 miles to the auto parts to get some oil absorb and 2 miles back to my house. In that 4 mile trip without beating on it the trans was logging (HPT) 218*. I couldnt imagine how hot it gets with a trailer or actualy playing around. Its got to be spending most of its time over 230* which I know is very bad for a trans. The only form of trans cooler on it is a small one in the small radiator they have, no external cooler. I told him it NEEDS a nice big external cooler on it and that it should NEVER get over 190* with that little motor.

Well 20 miles after he left my house the trans started slipping again and turned the SES light back on.

So is his trans shot? I'm thinking maybe. What a shitty design.

 

When you tow/carry a load, you need a LOCKING torque converter.
The 1 I use locks at 1200rpm, and trans run
s considerably cooler

 

If it has a 4l60e I'm willing to put money on it that it has a torque converter with a lock-up.

 

I think almost every trans in the last 20 years has had a lock up clutch from GM except a Th400. It is possible that this vehicle has a code in it that is not allowing the lockup to work. This is a fail safe with some codes. I would get it scanned to see what codes are in it first. Then clear the codes to see if it helps any. If the ses light comes back on, get it scanned asap to see what was recorded. Make sure to wright these codes down while doing this so you have a reference of what has happened. With the debris in the pan the trans it is probably not good. Vince