So this is my first time posting to a forum so I hope I am putting this in the correct place. I have a 2000 Chevy Silverado 1500 automatic manual 4x4. I was driving the truck and I lost third and fourth gear so me and my friend put the truck up on our lift pulled the transmission and I had it rebuilt by another friend of ours who was a gm transmission tech for 15 years or so. Once I reinstalled the transmission I have a really hard shift from 1st to 2nd I drove it for a day or so unfortunately I was kind of stuck driving it. We put it back up and dropped the transmission pan and found some clutch material in it, the guy who rebuilt the transmission was with me. We happened to have a used transmission even though I didn't really want to go the route we decided we would throw that in to get the truck going again and figure out the problem with the rebuild later. So we go threw all that and I still have the exact same problem completely identical hard shift between 1st and 2nd if you accelerate fast it shifts better but then the 2nd to 3rd shift is somewhat bad. This morning I got up early swapped out the mass air flow sensor and disconnected all the transmission electrical connectors and cleaned them and put dielectric grease on them and still have the same problem. I'm kind of at a loss it seems pretty far fetched that both transmissions would have the same issue but I really don't know what else to check from here. If anyone has any thoughts I would appreciate it thanks