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Old 06-27-2016, 10:00 PM   #88
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Re: 4L80E & TH400 Tech.

Originally Posted by kell490 View Post
Is there any advantage of using 6 over 5 disc direct drum? I know 6 will hold more lbs but is it worth the trouble. I'm using a 4L80E 34 sprag direct drum. I need to buy a aluminum piston the 2 sources I found said they could machine it to work with 6 disc or 5. It was my understanding that the 4L80E direct Drum has enough room for 6 disc if you remove the wavy and replace with steels.
Does your kit have the extra Friction & Steel?, If so....Have it machined for 6 Frictions. If not....Stay with 5 Frictions. And too add something myself.....I have GREAT luck using 5 Friction set-up's when using 4L80E High Energy Frictions!
There was a few TH400's that came Factory with 6 Frictions in the Direct Drum (Behind 500 Cadillac's mostly), The 4L80E drum is machined to the same depth.

Technically it has room for the Wave & 6 Frictions, Depending on the Machined Height of the Piston.
What you DO NOT want too do is use a late 4L80E wave plate with a Piston machined for 6 Frictions & a Wave Plate, The 4L80E Wave is super thin & can get logged under the "Lip" in the Drum & burn the Directs down, Break the Piston etc.
It is fine to run no Wave in the Directs......BUT, Along with Blocking the 3rd Accumulator, Can cause a overly harsh 3rd Apply.

More Direct Clutch/Drum info....
Sometimes, You can Omit the Wave, Stack the Directs with 6 Forward .077" Steels & 6 .080" Frictions with a 5-Friction Piston, It's a rare occurrence this stacks-up with the correct clearance (.010" per friction), Got to watch what you read on the internet....Just because it works on one Drum/Piston/Backing Plate combination, Does Not mean it will work for you!

As I touched on in our PM exchange....You NEED a Bleed Checkball in the Drum OR the Piston....But NOT both, Aluminum Pistons come in BOTH configurations! All 34 Element 4L80E Direct Drums have the Bleed in the Drum.
If you or others get a Piston with a Bleed Capsule.......It's a easy fix with a 1/4-28 Set-Screw.
Drill out the 2 tangs holding the Checkball in place, Remove the Checkball, Drill the hole all the way through with a 7/32" Drill Bit, Tap the hole with a 1/4-28 Tap.....NOT all the way trough!! You have to leave material for the Set-Screw too seat against, After you get the depth set right, Loctite the Set-Screw in & let sit overnight.

Aluminum Direct Piston with a Bleed Checkball, & the 1/4-28 Set-Screw.

The Same piston from the top, The deep spring pockets, The fact they can be machined, & They are very Stout are the reasons to use the Aluminum Direct Piston in any H/P TH400 or 4L80E build using High Rate return springs.
The Yellow circle is the Bleed, Between the 2 arrows is the material that gets machined for Piston/Clutch height.

This is a Stamped Steel TH400 Direct Piston with a Insert too control height, DO NOT use this Piston, They work OK on stock builds, Put Pressure to them & they can & will Fail!

4L80E Molded Stamped Steel Piston, Not suitable for High Rate Springs.
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