I have a 96 z71 1500 with the same trans but with a 383 crate gm motor. I had a race car shop but in a rebuild trans in it for me with all the best parts and great torque converter and it ran good. But as I started to floor it around to pass other cars I noticed the EXACT SAME THING! EVERYTHING YOU WROTE IS WHAT My truck is doing.. Let me know if you figure it out! hahaha
whats really funny is when I put all next exhaust and cats on it "true duals" I noticed it right away! its funny because you can still haul fast and accelerate just by lifting the throttle back just a hair and it wakes up and runs like its suppose to.. I have no idea. I used the good trans fluid Ams stuff. I think its a computer problem!?!
let me know what else you find!
thanks.. see if we can fix this!