I have a B&M Trans and convertor in my 85T/A.
I have a lock up switch to manually lock/unlock the convertor.
The problem is the lock up will work and very low speed but not at cruising speed(the revs dont drop at all)
Ive tried a new convertor,new solenoid,o ring on trans main shaft but no fix.The way i have wired it completely by passes all the sensor in the trans and the ECU so it is completely manually operated.
Any ideas guys
powermite

 

I would guess it's locking up but you can't tell because the torque converter is well past it's stall speed and there is not much difference between trans speed and engine speed. Try getting it in fourth unlocked and giving it just enough throttle so it doesn't down shift then lock it up and see what happens. Also try, with it locked up, giving it throttle and seeing how many rpms it goes up (without downshifting), then do the same with it unlocked. The rpms should raise more with it unlocked.