[VENGNCE]

I just picked an aluminum direct drum for my th400 and noticed a check ball in the drum behind the piston. Am right in assuming I dont have to drill a .060 bleed hole in this drum?

 

[racingtrans]

I just picked an aluminum direct drum for my th400 and noticed a check ball in the drum behind the piston. Am right in assuming I dont have to drill a .060 bleed hole in this drum?

If your using a trans-brake valve body, you will need to use the trans-brake release springs and yes, the bleed hole will have to be drilled if the the drum doesn't have the trans-brake bleed hole . Also this is it usually how it works, a drum with check ball, no check ball in the piston, drum with no check ball, use a piston with check ball. Hope this helps. Burt

 

[VENGNCE]

Whats the purpose of the check ball in this drum?

 

[racingtrans]

When the gear is releasing when the fluid pressure is released from that gear, it aids in disengagement. When you tear down serveral different years, we noticed that the check ball will either be in the drum without one in the piston, or not one in the drum but it will be in the piston.

 

[RCM Racing engines]

When the gear is releasing when the fluid pressure is released from that gear, it aids in disengagement. When you tear down serveral different years, we noticed that the check ball will either be in the drum without one in the piston, or not one in the drum but it will be in the piston.

Think you have this back words.....helps the apply piston,
keeps the piston from air locking while trying to apply
if it were the other way around you sure wouldn't need that there
.060 bleed hole, that bleed hole is recommended on all manual valvebody trans also, as it keeps the residual oil in the drum from appling the clutches in anything other than high gear.

hope this helps

 

[VENGNCE]

So I should plug the checkball in the piston since I have a checkball in the drum and drill the .060 hole in the drum. It is a transbrake valvebody btw.

 

[RCM Racing engines]

So I should plug the checkball in the piston since I have a checkball in the drum and drill the .060 hole in the drum. It is a transbrake valvebody btw.

Yes that is what i would do,,,Make sure you drill the .060 hole on the inside off the drum, out towards the outer lip seal surface but don't hit it, drill straight through...

 

[racingtrans]

Think you have this back words.....helps the apply piston,
keeps the piston from air locking while trying to apply
if it were the other way around you sure wouldn't need that there
.060 bleed hole, that bleed hole is recommended on all manual valvebody trans also, as it keeps the residual oil in the drum from appling the clutches in anything other than high gear.

hope this helps

Now that I thought about it, it makes sense. Bleeds the air out before fluid lockup. Never really thought about it until now, this is why I drill a 1/16" hole at the top of the reverse piston of a Glide, to provide a air bleed. Thanks! Burt

 

[Hutch]

So I should plug the checkball in the piston since I have a checkball in the drum and drill the .060 hole in the drum. It is a transbrake valvebody btw.

Have you ever seen a drum with more than 1 check capsule? I have seen a drum with 6 , so should I plug 5? Don't get confused with OEM applications , this is a race trans with constant system pressure.


Hutch

 

[F. RIZZO]

Have you ever seen a drum with more than 1 check capsule? I have seen a drum with 6 , so should I plug 5? Don't get confused with OEM applications , this is a race trans with constant system pressure.


Hutch

Yes plug the 5 ......................... sorry I had to LOL

Yea I'm still in the zone .........................

 

[VENGNCE]

Have you ever seen a drum with more than 1 check capsule? I have seen a drum with 6 , so should I plug 5? Don't get confused with OEM applications , this is a race trans with constant system pressure.


Hutch

Well, I was wondering why having the extra checkball would hurt. I have just never seen a th400 direct drum with the checkball, thought it was odd this drum had it. this is my first aluminum th400 drum to deal with. You guys have been great help, thanks to all.

 

[racingtrans]

We learn something new everyday, I never saw a drum with more then 1 check ball. Good info! Burt

 

[grinertech]

The ball in the drum is designed to vent resignal oil when is the drum is spinning, other words, to prevent a centrifical application of the high clutches while it anti rotates in 1st gear, or while parts rotates in neutral.

Only one problem, it is designed to work at normal highway driving speeds and does everything wrong in a racing application.

Here is what happens in a race car.

Low gear - The ball not placed far enough out to vent properly, or doesn't vent at all with a trans brake application. Anti rotation applies and eventually burns up the high clutches while accelerating through low.

Second gear - No problems because the drum is locked to the case and parts are not rotating.

Third gear - Oil pressure seats the ball. But what most people are not aware of is at higher RPM,s centrifugal force unseats the ball causing a pressure leak just when and where you don't need it.

I laugh when I see after market aluminum drums with as many as three ball. What are they thinking?

Anybody have a fix for this? or better yet, anyone ready to get off of their trade secrets ?????

 

[Hutch]

Have not seen that on the data logger , pressure seems pretty constant through the entire rpm range. What RPM do you see the check capsules become unseated Steve?


Hutch

 

[grinertech]

Have not seen that on the data logger , pressure seems pretty constant through the entire rpm range. What RPM do you see the check capsules become unseated Steve?


Hutch

It will be hard to see on a logger Hutch, thats because at high RPM,s the pump delivers ample oil, I suppose the pressure reading is taken at the plug on the side of the case, so there is ample oil there to. The manual valve is a bottle neck, and most cast iron valvebodys have a horrible third gear circuit. The leak is downstream and wont show up on the logger.

Now think out of the box, Measure the surface that the ball seats on in square inches. multiply that by line pressure and this is the force that holds the ball on the seat, now spin that drum and that ball becomes awful heavy, too heavy to stay seated, if you could take a reading on the in the drum you would see the leak.

I didn't see this problem until I got involved with a car that ran in the low six second range, Two problems showed up, The high clutches were dragging in low gear so bad the driver could feel the drag by the seat of his pants in spite of his 3000 HP engine.

Cured that, but was still nipping the clutches on the shift, removed the ball, plugged the hole, and end of clutch problem.

 

[RCM Racing engines]

It will be hard to see on a logger Hutch, thats because at high RPM,s the pump delivers ample oil, I suppose the pressure reading is taken at the plug on the side of the case, so there is ample oil there to. The manual valve is a bottle neck, and most cast iron valvebodys have a horrible third gear circuit. The leak is downstream and wont show up on the logger.

Now think out of the box, Measure the surface that the ball seats on in square inches. multiply that by line pressure and this is the force that holds the ball on the seat, now spin that drum and that ball becomes awful heavy, too heavy to stay seated, if you could take a reading on the in the drum you would see the leak.

I didn't see this problem until I got involved with a car that ran in the low six second range, Two problems showed up, The high clutches were dragging in low gear so bad the driver could feel the drag by the seat of his pants in spite of his 3000 HP engine.

Cured that, but was still nipping the clutches on the shift, removed the ball, plugged the hole, and end of clutch problem.

GOOD To know,,, thanks for sharing............................

 

[racingtrans]

Very good stuff really enjoy reading this! I also have heard that with higher RPMs some transmissions have been known to have clutch apply through Centrifuging residue fluid left behind the apply piston by residue fluid being thrown against the inside walls of the inner drum piston area thus pushing the piston partially applying the clutches? It would seem that the 1/16" hole drill in the drum and the heavier return springs should resolve any issues with this when a trans-brake valve body is installed. Burt

 

[SILVERFOXTRANS]

Most important note in the info griner posted is the "if it releases at all with a transbrake" the high drum goes from being clamped, to 6000 rpm in a split second, there is little time for the drum to exhaust, especially if just the ball and VB are doing the work...and outboard exhaust hole is always a critical item for fast/clean TB use - don;t care who's vb you use. That is just my advice.

As for the ball unseating at high rpm, I could follow that theory possibly. I would say it just make good sense to block the ball in pure racing application, not much to loose and might learn something, let you know.

 

[grinertech]

Very good stuff really enjoy reading this! I also have heard that with higher RPMs some transmissions have been known to have clutch apply through Centrifuging residue fluid left behind the apply piston by residue fluid being thrown against the inside walls of the inner drum piston area thus pushing the piston partially applying the clutches? It would seem that the 1/16" hole drill in the drum and the heavier return springs should resolve any issues with this when a trans-brake valve body is installed. Burt

You got to remember when the trans brake is applied the high gear clutch is applied and the piston is full of oil and "under pressure", its not residue you have to deal with, its real oil. The ball is seated at this point and offers nothing as far as any help.

As the car launches, the high drum begins to anti-rotate. The heavier springs aid in exhausting some of the oil out through the trans brake valve, but the car is moving before the clutches have a chance to release clean.

As the drum spins up or anti-rotates through low gear, the remaining amount of oil is trapped in the drum by centrifugal force. The clutch tries to reapply but the 1/16 drilled hole gives the oil a path out.

I might add, the faster the car 60 foots, the worse the problem becomes.

I might also add, you guys who want to "neutral in the traps", the 1/16 hole does exactly what it is supposed to do, let the oil out of the drum. Allowing it to spin out of control and explode.

 

[grinertech]

Most important note in the info griner posted is the "if it releases at all with a transbrake" the high drum goes from being clamped, to 6000 rpm in a split second, there is little time for the drum to exhaust, especially if just the ball and VB are doing the work...and outboard exhaust hole is always a critical item for fast/clean TB use - don;t care who's vb you use. That is just my advice.

As for the ball unseating at high rpm, I could follow that theory possibly. I would say it just make good sense to block the ball in pure racing application, not much to loose and might learn something, let you know.

What do you mean "don;t care who's vb you use". Compare a valve body to a cylinder head. only one flows air and the other flows oil.

You have only Nano-Seconds for the first and most important event to take place.

That Is, "Get the the oil out of the drum the proper way, through the valve body and out the trans brake valve. The better it flows, the better the trans brake works. This means a clean, simple and efficient oil path to and from the high drum".

If anyone running a 3 speed is burning high gear clutches, In most cases, look no farther than the valve body.

Just an opinion from me, the guy that invented the trans brake.