With a FLT Vacuum Modulated trans you can't tune shift points or line pressure correct?

I did some searching here and at HPT forums and from the information i've gathered shifting "is what it is" with the vacuum mod (which is still a great performance mod at any power level).

 

you tune when it shifts and that's it. the line pressure and speed of the shift are vacuum controlled

 

awesome!! Thanks

 

Yup, it's a bit weird too. DON'T let off right before the transmission shifts. I know some people do that, and I did it a couple times too. I find if I do that mine shifts really soft, and my point of trying to be easy on the transmission turns into something harsh for the tranny.

 

If I'm not mistaken you can still control shift time. Vacuum modulator on replaces the electronic pressure servo so it only can controls the actual line pressures. Shift RPM and Shift time is controlled by the shift solenoids which you still have control of via the PCM.

 

doesn't the vacuum modulator have an adjuster screw inside the tube (you remove the vacuum hose and stick in a small screwdriver and turn) for controlling the speed/firmness of the shifts?

 

that would be good to know because I always hear people barking 1-2 shifts and I have never done that with my trans.

 

Old school external Vacuum modulators had this feature. Ones in the new transmission don't. If you want to tune the shifts with them you have to adjust the pin length on the modulator and its internal to the tranny.

 

oh.... I see......