Boost and turbo 400 vacuum modulator--do I just use a check valve?

[Steve]

I am putting a turbo 400 in my car and the I am curious what I need to do about the line to the vacuum modulator on the turbo 400 to keep boost from being an issue. Do I need to just use a check valve in line? Thanks for the help.

 

[blackplague]

Just install this little valve in line

I am putting a turbo 400 in my car and the I am curious what I need to do about the line to the vacuum modulator on the turbo 400 to keep boost from being an issue. Do I need to just use a check valve in line? Thanks for the help.

Install this:

Trans Go part # VBP-VAC

For trans’s with vacuum modulator
and Supercharger
or Turbo

Vacuum/Boost Bypass Kit: All trans with
vacuum modulator and supercharger or Turbo.
Prevents boost pressure from
causing runaway line pressure

Look up Trans Star, D&E Automotive, Slawson trans parts. One of those guys will have it.

 

[Steve]

Thanks!

 

[INEEDAGN]

They also made mechanical modulators for the 400s. I beleive they were used in diesel applications. Uses a cable similar to a TV cable.

 

[87buickracer]

Transgo vacuum bypass (VBP-VAC)

bypass is best part for the money as stated in my turbo 400 build up..
Install with vacuum modulator..

 

[Frankensteeen]

Transgo vacuum bypass (VBP-VAC)

bypass is best part for the money as stated in my turbo 400 build up..
Install with vacuum modulator..

I know this is an old thread.

Like to revive it !

Installed this trans go valve , now it shifts great at 5500 rpm.

The problem is ONLY 5psi of Boost.

Any ideas to get this to shift with full boost. Was at 20+psi on a mbc.

Thanks

 

[Frankensteeen]

I know this is an old thread.

Like to revive it !

Installed this trans go valve , now it shifts great at 5500 rpm.

The problem is ONLY 5psi of Boost.

Any ideas to get this to shift with full boost. Was at 20+psi on a mbc.

Thanks

With this hose pinched with vise grip pliers can get the 20+psi.

Really wanted this to work, but just creates to much bleed off. But the transmission dose shift at wot now.

Anybody have a solution to this ?

..... I want WOT shifts , with AUTOMATIC SHIFTING th400 transmission and full boost .

 

[Frankensteeen]

Edit to add , this was pressurized with air compressor. To test for boost leaks. The Largest leak IS this bypass vent valve by trans-go.