Recently replaced the 700R4 transmission in my 84 Firebird with one out of a 1992 Monte Carlo, had it rebuilt and installed and finally had to unplug the converter lockup harness because it locked up at any speed in any gear. How can I fix this problem? Do I need to install the lockup kit used in hotrods?

 

Did the old transmissions lockup work properly? It should not lock unless commanded to and since the transmission seems to work correctly when disconnected the fault is likely with the car.

 

Lockup worked properly on original 700, my thinking was that any 700r4 would work on any vehicle factory equipped . Maybe any difference in governor & input & output sensors is causing the problem, not sure.

 

This is a shot in the dark - I'm certainly not a tranny expert ...

Some 700R4's had a Normally Closed (NC) switch inside for the lockup, and some had a Normally Open (NO) switch. Maybe it's the case where your 1984 ECM is sending the wrong signal (or sending a signal at the wrong time) to that newer 1992 tranny. I'm not 100% sure how that all works, and what signal or when a signal is sent to the tranny.

Reading the sticky in the carb forum on the TCC Control might help - https://www.thirdgen.org/forums/carb...c-control.html - and you might ask on the tranny forum.