I got a good deal on a street/strip th400 that I would like to take advantage of. The only problem is that it is a manual/automatic, I was told on the 400 if you have a turbocharger you need to use a full manual because they use vacuum to know when to shift.

If I just drive "normal" it should shift fine since there'll be no boost. With a manual/automatic shift kit I could still shift it under boost right? I would just have to make sure and shift it and not forget that it won't shift on its own. Am I correct on this? I was also thinking, couldn't I just use a check valve when manually shifting it so the tranny just thinks there is 0 vacuum. Whenever you are @ WOT you are @ 0 vacuum anyway.

 

i have the same setup...vacuum hose with a checkvalve...it works fine. I dunno where these myths come from...mine is forward vb...manual/automatic just like yours

 

Are you just using the check valve or do you also have a "vent" in between it and the modulator? I was thinking just using a .027 welding tip to bleed off vacuum while that check valve is closed.

 

just a check valve left over from the vac. mod kit my 4l60e had......it is closed under vacuum and opens under boost