Well it's not in an LS1 car, it's in his 1997 S-10. I think it's the same tranny though. It's a totally stock V-6 auto. The problem is it shifts so hard after the truck has been driven for 30min or more it breaks the tires loose on Every upshift. He had the fluid changed, had it checked out and they said there was no problem of course. Just wondering if anyone's had these type of problems and might help us pinpoint the problem?

 

See if you can get a read on the tranny temp. If the tranny gets real hot it goes into the abuse mode and has real hard shifts. Maybe the cooler lines are crimped or plugged.