In need of major help.

I own a 1986 toyota supra, and I'm having some difficulties with the torque convertor engaging / disengaging.
Here's my problems, at times the car will shift properly, from 1-2-3, then presss button and overdrive. But it will not kick down. Other times it will rev up to about 4500 RPM before shifting with alot of stall between 1500-3000 RPM (like the torque converter isn't engaged or stuck inbetween...) I've been thinking ECM? The transmission is fine, it's been rebuilt by the best transmission shop in my city, and this problem was still there even before the tranny rebuild. Any comments please??

any help? the car is always shifting at different times, it has a power mode button too, might have something to cause the problem?

Does the car have the original size tires and wheels? If not, the speed sensor may not be detecting the correct speed versus engine rpm and/or it is going bad. As a result, your speedo and odo may be off.

In these year cars they are usually mechanical/electrical that are ajdusted by switching out the little gear at the end, but ask the tranny shop to be sure.