A while back I was getting on the freeway and went to speed up to merge on, and my transmission felt like it shifted into neutral. I pulled the code and it revealed a transmission slip (don't remember the code). So I bought a used transmission from a place that sells engines and transmission with 80,000 miles or less (supposedly from Japan). So installed the new to me transmission same thing no high gear. pulled it back out exchanged it for another one. Installed it and same thing NO high gear. Now I am thinking that there is something wrong that is not the trans. Someone please help. I need my truck back up and running.
It is a 2000 Silverado 5.3 4x4

 

have you found the problem? My truck is doing the same thing, I have changed the solenoid new valve body. I'm at my wits end don't know what else it could be

 

3 4 clutch pack is shot. Time for a rebuild

 

2001 blazer transmission 4l60e. Soon as it gets hot it starts slipping. But I can shut the blazer off in N then start it back up then it act like its normal. Please help going nuts on this