th400?

[boostedblkbeast]

I am going to be switching to a th400 trans and would like to know some suggestions about what trans yoke to go with. Also, I know that th400 shifts according to the kickdown switch and engine vacuum, but our motors only make vacuum untill boost overcomes that, so do I need to put a check valve in between or is their another cure to the problem. Also, any other tips or tricks to the tranny as far as install or anything related would really help. thanks

 

[boostedblkbeast]

No one has any comments.

 

[Louie L.]

You need a stock TH400 yoke and a combination universal joint to mate it to the stock drive shaft. Aftermarket yokes can be purchased also from most of the trans / driveshaft builders.The drive shaft may need to be shortened, but its different from car to car.
Most of the TH400s in Buicks are Manual valve body , so they have to be manually shifted. It also eliminates any problems that may arrise with the vaccum issue on a full auto.

There are some out there shifting automatic but i dont know much on how to do that.

 

[49-blues]

Would the same apply to a 350 trans? And how about if using a transbrake?

 

[Louie L.]

It was my understanding that there are no transbrakes for a TH350. But i may be wrong. The principles are the same. Im sure that you can have a manual valve body 350. If you wanna keep it full auto the same above isues will have to be planned for.

 

[CTX-SLPR]

To retain a full automatic transmission you will need to replace the vacuum modulator with a mechanical modulator. The mechanical modulator uses the cable to determine engine load via throttle possition instead of engine vacuum like the stock vacuum modulator. If you search on here for there, I think sometime in the past I found a source for one back when I was going switch pitch.
There are transbrakes for just about every tranny you can think of out there so be it TH350, TH400, even AOD... you can get one, however depending on the tranny design some of them are harder on the tranny than others.
The nice thing about the TH400 is that it does not use a kickdown linkage like a TH350 or the TV cable on a TH200-4R. However you need the throttle mounted switch that tells the tranny to downshift based on throttle pedal possition or an aftermarket Lokar one that is kind of like a divorced style linkage for the kickdown switch but its still uses a cable.
Just my thoughts and knowledge on the subject,

 

[azgn]

why would you switch to a 400 unless for a race car? (in which case you will want a trans brake w/ a manual valve body?)

a 2004R is a much, much better trans for a street car (think 4th gear and lockup converter....not available on a 400)

 

[CTX-SLPR]

I'll have to disagree on the lockup, there is a TH400C that has a lockup converter, as to how durable it is, I don't know. But you are right, a TH200-4R is a much better street transmission with its overdrive, though if you are doing a hybrid a TH400 could be just as viable of an option as it is cheaper to build, especially to take power.