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Old 02-09-2016, 09:17 PM   #45
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Join Date: May 2009
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Re: 4L80E & TH400 Tech.

Originally Posted by picklito View Post
1970 TH400: I'm at .125" using a new plate from Superior and all 6 original check balls. I want to go a little firmer... enlarge the hole or start removing check balls?
Do you know what style Direct Drum you have...Roller Clutch or Sprag type???

A Intermediate Roller is quite a bit weaker than a Intermediate Sprag, A '70 model "should" have a Sprag type Drum.

Roller Clutch....NO larger than .125"! If you do.....The risk of Roller Clutch failure is high.

Sprag....You can go out to .140".....With the 2nd Clutch checkball in place & a Active 2nd accumulator.

Do not remove checkballs....The Reverse checkball being an exception when dual feeding the directs.

The checkballs job is to route clutch feed oil through the orifice, If you remove it, Feed oil will freely pass through both the orifice & the hole the checkball is suppose to check. You end up with a effective feed hole size of over .300" or larger.
I have fixed too many broke units with B&M/TCI shift kits (That delete checkballs) to ever recommend doing this on a street transmission.

The ONLY time I omit CB's other than reverse, Is on Reverse Pattern Manual Valve Body (RPMVB) units, And RPMVB with a Trans Brake. However these competition units don't take a standard plate, They only have the Feed holes, The CB holes are eliminated.

Here is a pic of a RPMVB/Trans brake plate to show the huge difference from a standard plate.
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