One of my buddies is dropping a twin turbo small block in his car with a turbo 400. while we were installing it the question came up of what the boost would do to modulator and the trans operation. I've built a lot of trannies but never for a boosted application and I couldn't give an honest answer. Any body know what mods we need to make if any

 

I need to know the same thing...

 

You will need the TransGo 400-3 full manual Performance Shift kit. This will still use the vacuum modulator. You will need the vacuum bypass from TransGo when using a super charger or turbo charger. This will still allow the modulator to function and keep the front pump alive. If you want to keep it a full automatic, then you will need the vacuum pump and bleed off assembly from a vehicle that has used a diesel. This can work very well. It will take a little home work though to find these parts.

 

dont mean to hijack the thread but what do I have to do for a 200r4 if i wanna keep it full automatic. I know some of the 200r4 were used by grand nationals and maybe thats my answer but i would like to upgrade to something aftermarket. Like u said u need a pump from a diesel and maybe i need a pump from a grand national but i was gonna go with a 13 vain upgrade. Now I'm so confused. Please any advise would be helpfull

 

2004R is a different animal you only need the TV cable hooked up it dosent care about boost or vaccume

 

Thank you so much x1000.

 

Stay with the 10 vane setup, as the pump has to be modified to get the benefits from the 13 vane setup. If you plan on using the 2004R with a lockup torque converter and you plan on using it to get WOT TC lockup, then stay with the 7 vane setup (if you can find it, if not the 10 vane will do) with the TransGo Hi-Rev steel rings for the front pump, and get the drainback/feed tube that goes on the front pump from Precision Industries. This can double the life of the torque converter clutch when using TC for WOT lockups.

 

I've just dropped a TH400 into my turbo car and have been stuck with the same problem.

Will a manual valve body install solve my issue, leaving teh vacuum modulator connected to the plenum with a check valve to stop boost hitting the trans? Or does that not matter so much?

 

As I stated earlier. You will need the TransGo 400-3 full manual Performance Shift kit. This will still use the vacuum modulator. You will need the vacuum bypass from TransGo when using a super charger or turbo charger. This will still allow the modulator to function and keep the front pump alive. If you want to keep it a full automatic, then you will need the vacuum pump and bleed off assembly from a vehicle that has used a diesel. This can work very well. It will take a little home work though to find these parts. The front pump will last many times longer when using a vacuum modulator.

 

OK, so if im just using the vacuum modulator to keep the pump alive and not to aid in shifting (since it will be full manual), am i able just to connect the modulator to a vacuum pump? Or is the variable nature of engine vacuum still required even though the shifts are selected manually.

Thanks for the help.

 

Again, if you want to keep it "full automatic", then you will need the vacuum pump and bleed off assembly from a vehicle that has used a diesel with a TH350/400 transmission. The vacuum must drop with throttle opening, to change line pressure. This will keep the unit alive.

 

No. I'm asking if the vacuum modualor needs to be hooked up to a vacuum pump if I'm using a manual valve body.

I guess I'm asking what does the vacuum modulator do/control OTHER than the shift points since I am running a manual valve body. Does it also control the output of the front pump? If so would a static vacuum level from a vacuum pump work to keep the pump active?

Thanks again.

 

The vacuum must change with the rate of the throttle opening to match motor torque. When vacuum goes down, the line pressure must go up to match the torque of the motor. This is what keeps the front pump alive. You cannot keep the vacuum the same at different throttle openings.

 

ah ha. THankyou for clearing that up for me. Cheers