Heys guys, Recently got my hands on a 2003 Silverado 5.3 2wd for dirt cheap. Has 263k highway miles, motor runs excellent and truck is super clean. Only problem I am having is trans shifting 1-2 wants to "slip" under acceleration. Feels like it is shifting twice just going into second. If you are going slow barely using the throttle it seems to shift fine but if you try to accelerate at all the 1-2 shift has this problem. Other shifts feel fine. I am not sure if the tranny just needs to be rebuilt, bad solenoid, or maybe a torque converter problem? Or maybe a drive shaft or rear end problem? Any help would be greatly appreciated guys. Thanks.

 

I had an 03 z71 that had 40k miles on it when I bought it that shifted like that. Feltlike it would shift into second, then clunk again feeling like it shifted twice. Never figured it out. My grandpa has that truck now and it has 100k miles still going strong.

 

Sounds like the band is wearing. This can be determined by measuring the end play on the servo housing. While holding a ruler near it, press on the cover with a crowbar and estimate how much it moves. Spec is less than 1/8". By 3/16" it will start slipping and around 1/4" 2nd and 4th are likely gone.
Bunch of people have gotten more life out of their trans (10K miles?) by lengthening the servo pin. But if you plan to keep the car longer, it is time for a rebuild.