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Old 01-17-2011, 12:56 PM   #1
VENGNCE
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Default Aluminum drum bleed off ??

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?
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Old 01-17-2011, 01:07 PM   #2
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Default Re: Aluminum drum bleed off ??

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Originally Posted by VENGNCE View Post
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
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Old 01-17-2011, 01:27 PM   #3
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Default Re: Aluminum drum bleed off ??

Whats the purpose of the check ball in this drum?
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Old 01-17-2011, 01:41 PM   #4
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Default Re: Aluminum drum bleed off ??

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.
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Old 01-17-2011, 08:22 PM   #5
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Default Re: Aluminum drum bleed off ??

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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
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Old 01-17-2011, 08:36 PM   #6
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Default Re: Aluminum drum bleed off ??

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.
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Old 01-17-2011, 08:41 PM   #7
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Default Re: Aluminum drum bleed off ??

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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...
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Old 01-17-2011, 08:54 PM   #8
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Quote:
Originally Posted by RCM Racing engines View Post
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
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Old 01-17-2011, 09:04 PM   #9
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Default Re: Aluminum drum bleed off ??

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Originally Posted by VENGNCE View Post
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.


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Old 01-17-2011, 09:45 PM   #10
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Default Re: Aluminum drum bleed off ??

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Originally Posted by Hutch View Post
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 .........................
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Old 01-17-2011, 11:27 PM   #11
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Default Re: Aluminum drum bleed off ??

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Originally Posted by Hutch View Post
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.
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Old 01-18-2011, 06:50 AM   #12
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Default Re: Aluminum drum bleed off ??

We learn something new everyday, I never saw a drum with more then 1 check ball. Good info! Burt
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Old 01-18-2011, 06:55 PM   #13
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Default Re: Aluminum drum bleed off ??

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 ?????
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Old 01-18-2011, 07:58 PM   #14
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Default Re: Aluminum drum bleed off ??

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?


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Old 01-18-2011, 08:53 PM   #15
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Default Re: Aluminum drum bleed off ??

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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.
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