Modifying Full Throttle Upshifts BW M12

Frank is correct but I would like to add that the tranny will kick down back into first at full throttle at up to about 20 to 25 mph. At closed throttle coast down it will drop back into first gear at about 10 mph. Of course you can always shift manually but with the modulator adjusted as described there would be no reason to.

The only thing you never want to do is to manually drop the transmission back into second gear to slow the car down. The friction material on the front band is very thin and not made to act as a brake. At closed throttle the transmission pressure drops to minimum immediately so the band ( which, when activated/applied, is what provides 2nd gear ) will have minimal activation force. This causes a fair amount of slippage as it tightens on the front drum. Just the opposite is true at full throttle as the engagement pressure is at maximum and there’s minimal slippage.

Try another couple of turns. You’ll want to move the full throttle upshift point up another 200-250 rpm’s. You’ll know if you’ve gone too far. The improvement will be significant. You’ll also note that the full throttle 2-1 kick down speed will go up a little but you’ll be able to drop the shifter down manually into first gear at a little higher speed than the kick down will allow.

Did you get a chance to do any additional tweaking, or did you reach a happy place setting ?

Yes, crank in a few more turns. As you go in you’ll find that the pressure and shift points will move up more quickly as you turn the adjustment screw inward. If you go too far you’ll know it as the shift points will be too high. If that becomes the case then back out one turn at a time until you get to a full throttle upshift at about 4900 rpm assuming you gave a stock cam. There will be a world of difference in the performance of the car and you’ll be materially extending the life of the transmission as well. There will be little to no slippage during the shifts. It will shift like you installed a shift kit !

Edited by george w - Jun/09/2022 at 9:56am

Sorry to hear that the set screw stripped out. It may be possible to back it out all the way and replace it. I’m wondering if your tach is reading accurately. By manually using first or second gear will the engine rev to at least 5000 rpm or a little beyond ? I will say that as you turn up the pressure the set screw is pressing against a spring so the effort to turn it increases. I’m surprised it stripped out though. Maybe just the slot got a little messed up so maybe a slightly larger screwdriver blade may get you another turn or two.
Just as a thought, is the electric kick down switch above the gas pedal in proper adjustment ? It has a ratcheting type of self adjusting mechanism. The TSM details the procedure. It only takes a few seconds to reset it. No tools required.