To start off I have a 2002 Silverado 2500hd 6.0 2wd with a 4L80E. The trans was just rebuilt a few weeks ago. My problem now is when the trans is hot (trans temp gage reading 165' or higher) the trans will hunt gears it will be in 4th and drop to 3rd then back while driving steady at 45 or above at highway speeds it will shift back and forth and finally go into 3rd and stay there untill I slow down. If the trans temp is lower than 165 it does just fine. Any assistance would be greatly appreciated.

 

I have a 4l80e as well.

Mine was doing that as well when I bought it and would clunk horribly when it was warm when the torque converter locked up.

Anyways, long story short, through a fluke the dealer ended up flushing the tranny 3 times over the course of 2 weeks and it is perfectly fine and shifts like a dream now.

I'm thinking that maybe when the tranny was rebuilt there was some gunk left behind. It may be good to flush it out just in case anyways.