TH400 Upgrade

[adey]

Hi all
I am building a th400 from a 454 chevy 1982 which has steel pistons.
I have bought a pre 71 direct drum and a 34 element sprag to go with the upgrade. however i am confused , the repair manual says that the steel pistons do not have check balls, and the drum for the 34 element sprag does not have a check ball either. There is a tiny hole just above where the check ball is located on the old drum, ? do i need a piston with a check ball, and do i need to block this hole, or will it be ok with or without a check ball in the piston.?

If i need a new piston , any idea where i can get one from ,

best wishes Adrian.

 

[Gerry]

Hi all
I am building a th400 from a 454 chevy 1982 which has steel pistons.
I have bought a pre 71 direct drum and a 34 element sprag to go with the upgrade. however i am confused , the repair manual says that the steel pistons do not have check balls, and the drum for the 34 element sprag does not have a check ball either. There is a tiny hole just above where the check ball is located on the old drum, ? do i need a piston with a check ball, and do i need to block this hole, or will it be ok with or without a check ball in the piston.?

If i need a new piston , any idea where i can get one from ,

best wishes Adrian.

It doe not matter really. They are there to stop residual pressure which stops the clutches getting a slight apply. You can go either way it wont hurt. Withou the check balls the clutches will come on slighly harder and quicker.
Gerry

 

[Screaming Metal]

It doe not matter really. They are there to stop residual pressure which stops the clutches getting a slight apply. You can go either way it wont hurt. Withou the check balls the clutches will come on slighly harder and quicker.
Gerry

Gerry is perfectly right, they're not really necessary. Whenever the spool moves into position, fluid is thrown onto that side of the spool and the pressure goes thru the hole and 'bam', you have lockup on the clutch. The old Lenco's are really a series of clutches instead of really being a trans. where you shift gears....they are operated by locking clutches at certain times to achieve max. acceleration.

Turbo 400 stuff can be bought at any trans. parts place, ie, B&M, TCI, National Trans, places like that....

Hope this helps....

 

[adey]

Well thank for that guys , i have spent all day messing with the transmission, and trying to set up the clearences, i have altered the valve body and removed a seal to duel feed the direct drum. I am hoping that it will not be too fearce in the t bucket?As i still wish to have auto control.

Gerry are you going the iva route? or have you been lucky with a old car? i have no option but to go iva route.

Adrian