Ive got a 2003 Chevy 2500HD with a 6.0 and the 4L80E tranny. Here lately i've noticed that if i get the truck up to around 80mph on the interstate or something, when i slow down and take off again, the transmission shifts HARD and earlier than it should. It only starts actin up after i get up above 75 or so. Transmission temp is normal and i had i had it flushed around 10.000 miles ago. What do yall think?

My sons truck is doing the same thing. 01 2500HD 6.0L 4X4. The temp is fine and it will shift clean through everything, until, he gets up to around 65+ then have to slow down and while its shifting UP again it shifts HARD. I am sure yours shifts just as hard. This is REALLY hard. am i right?If he turns the truck off for about 2mins or so it goes back to normal. He told me a while back that it seems to be shifting harder SOONER than it normally would. It would normally do it at a little under 200degrees. Now it will do it almost at whatever temp. If anyone can help us out PLEASE do so. Thanks, Ghost

Almost sounds like a reflash is needed. Check with local dealer.

My sons truck is doing the same thing. 01 2500HD 6.0L 4X4. The temp is fine and it will shift clean through everything, until, he gets up to around 65+ then have to slow down and while its shifting UP again it shifts HARD. I am sure yours shifts just as hard. This is REALLY hard. am i right?If he turns the truck off for about 2mins or so it goes back to normal. He told me a while back that it seems to be shifting harder SOONER than it normally would. It would normally do it at a little under 200degrees. Now it will do it almost at whatever temp. If anyone can help us out PLEASE do so. Thanks, Ghost

Sounds exactly like mine. Does he have a programmer? Ive been aiming to put the stock tune back in mine but i havent had time to try it. Me and a buddy took my truck up to Indiana today to fetch a rear end for his truck. After getting off the interstate it acted in the usual way. Shifting hard. Sometimes its not too bad but sometimes its down right violent. I'll try reloading my stock program and see if that makes a difference.

If returning your programming to stock doesn't help try unplugging the trans connector to trans,starting vehicle briefly,shut off and erase the codes from running with trans dissconcted. When vehicle is started with no power to trans the epc solenoid will cycle to full pressure because of lack of its 5 volt/1 amp signal that controls the position of its pintle valve. I have seen epc's that stick causing hard shifts on these trucks and I have also seen the motor throw a high misfire code on a particular cyl which can put the computer in a protective mode which defeats lock-up and turns up line pressure causing later harsh shifts. Sometimes the vehicle has to be driven with a scanner in place until it acts up to see the problem if its a intermittent electrical issue. When your truck starts shifting like this pay particular attention as to weather it still goes into tcc lock-up or not,it will help if someones trying to diagnose it,Smitty