Tranny Problem

tranny upshifts harshly after I have driven it hard along time or after hauling a heavy load Im gettin a hard thump/pull as it goes from 1-2 and 2-3 ... it seems to do it more after its hot...still i feel an unsmoothe shift especially from 2-3 check engine light comes and goes (might be o2 issue, high altitude travel elevations from 4500- 8500 ft )Fluid and filter has been changed Fluid full 90,000 miles 99 gmc sonoma 2wd 4l60e ( i believe) anyone have similiar experiences??

when was the last time you changed the fluid??? it should be changed every 30,000.. you should pull the dip stick and smell it. If it smells burned or if the fluid is very dark you will want to get it checked out.

seen it plenty, unfortunately.. chevy had a prob with the valve body in those trannies. call your local gm dealer. they'll have 30 of um in stock to the tune of about 5 bills. sorry

Ive changed the fluid and filter...the fluid that came out was fairly decent... I've heard about the valve body problem on this tranny... so that means what I need is a new valve body?...Im wondering if ive damaged other parts from the harsh upshifts that did happen... Ive discovered that when I drive long enough to were I know its going to upshift harshly...which it only does after a long drive...If i turn off the engine and restart it 3 seconds later it shifts fine...

seen it plenty, unfortunately.. chevy had a prob with the valve body in those trannies. call your local gm dealer. they'll have 30 of um in stock to the tune of about 5 bills. sorry

The valve body needs to be changed or the whole trans? That sounds like the same problem I'm having. And are you talking about $500 or $5,000?