I'm new to this site so bare with me! I just bought a 1991 GMC 2500 (350 TBI, 700r4) from a friend of mine. I got a great deal because my other truck is down for the count. About 9 years ago, it jumped time. My friend put a new chain and gears and cover on it. Because of his job, he had to stop working on it. He never got around to ever finishing up the truck and it has sat there ever since. It has been outside with the engine wrapped up and the front up on jack stands. I have got it running pretty well and it has cleaned up nice. Everything works and seems to be doing fine. Except the transmission. He had it rebuilt about 5,000 miles before the truck was parked. I changed the fluid and filter on the trans right after I got it and have checked and re-checked the fluid levels and they are correct. The problem I'm having with it is that it don't shift right. It shifts into 2nd way too early and seems to shift through the gears too quick. It shifts 1-2 at about 10mph with regular acceleration. Also it doesn't seem like it downshifts right either. I have adjusted the TV cable the best I can according to what I have been told. What unique problems would be linked to it having sat for so long? Is there something that I can take apart and clean or check? Is there any additive that you would recommend? I would love to have the money to have it taken to a trans shop but right now I’m pretty short on money so anything I can do on my own would be great. Thanks in advance.