727 slipping

The throttle pressure linkage (kickdown linkage) (spring included) will not affect it at all. You could remove the throttle pressure linkage all together and the transmission would still take off just fine. The throttle pressure linkage varies clutch pack pressure and affects the shift timing. Sorry to say but it sounds like the rebuilder either folded a seal over backwards or nicked it in a clutch pack or possibly didn't check the clutch pack clearance and it had way too much. Could also be a valve body problem but it sounds more like a clutch pack issue. Call Frank on Monday. He's a good guy and will take care of it I'd bet.

Just noticed you said a local rebuilt it. He's who you need to talk to, not Frank.