I just picked up an 85 z28, and of course it has transmission problems. It will not upshift in part throtte until around ~3600 rpm in all gears, and the shift is very hard, tire chirping. If you give it full throtte, it will shift around ~4800 rpm. It also has no kickdown.
I just replaced the TV cable with a new gm unit. Adjusted it as per directions on this site. upshift problem is still the same, and now the trans tries to downshift, but it just shudders. Its weird i have all the gears, but it just wont shift until high rpms.
Anyone have any suggestions? thanks in advance.

 

Slipping band?
bad TV cable/wrong geometery?

 

With the car running, detach the tv cable at the throttle body and give it a few quick yanks to free what ever might be stuck in the valve or a valve port. Change the fluid and filter or have the trans flushed. It could have a high or failing converter. It could be a failing governor? Just a few things to check. Also what color is the fluid and does it smell burnt?

 

Yea, i was thinking that the valve might be gummed up-the car has been sitting for four years. The fluid looks ok, but it does smell a little burnt. Im going to go get a flush and see if that helps out things a bit, ill also see if the governor is sticking or not. Basically im tryin to check everything i can before i take it to a shop, because i know thats probably goin to hurt my wallet.