On an 89 Firebird with 350TPI & 700R4 when is the car supposed to shift and lock up? I just changed to 3.73's from 3.2? gears and the car is great off the line but while driving normally at 30-40mph its a dog. At that speed its in 4th gear and the TC is locked. If I mash the peddle it down shifts as it should and goes but part throttle acceleration doesn't happen. Can I adjust the shift points to accomodate the new gears or keep lock up from happening until a certain RPM is reached? Any thoughts / comments would be appreciated.

 

The lock-up is based on VSS input, not RPMs. You could reprogram the PROM to lock-up at a higher speed, though.

I suppose you could do something RPM dependant, too. But, now I'm way, way over my head.

Hmm, there is probably some TPS input there, too. Perhaps lower the TPS voltage thresshold.

Never mind, I'm over my head.

 

That makes sense to me. So by changing the gears the VSS thinks I am going faster than I really am which is causing lock up to occur sooner.