Question for TH-400 builders:

[trikbag406]

I have a th400 with reverse manual trans-brake valve body in my Vega.I already know I built the clutch stacks too tight (10-20 thousandths per stack),because when you wing it to 4-5000 in neutral,the car lurches forward,kinda like the forward clutch is too tight.My question,if you haven't guessed,is what would be a good baseline clutch stack clearance for each set in the trans? I'm simply gonna dis-assemble the trans,check the clearance,and machine the clutch pistons,if possible.Thanks in advance ladies and gents-Lew.

[Mark Yacavone]

.010 per friction unless you are into some weird situation with a T-brake.

[Tom Goldman]

Most TH 400 trans brake applications require .060-.080" clearance.
even with that clearance there is still considerable drag in the pack.
Most builders use o-ring segments slightly thicker than the disc to stand off the steel plates from the discs to reduce drag.
4 to 6 segments per disc,cut so they just fit into the steel plate slot in the drum.
the disc and centrifugal force will keep them in place.
most 400 brakes also require an .030-045" bleed hole in the drum and heavier piston return springs.

The drag will be even worse if you are using metallic waffel type discs.

[trikbag406]

Thanks guys,appreciate the info.Tom I've heard of the o-ring trick before,just have never seen it myself.It makes good sense,and I'm game,it doesn't take a magic wand to make it happen,and yes,I'm using waffle clutches,so I really ought to start cutting up some o-rings

[trikbag406]

Oh,and I almost forgot,the drum has already been drilled,and yes there are some un-Godly return springs in this thing,my home-made snap-press didn't even want to compress it enough to get the snap-ring out.

[Alan Roehrich]

The o-ring most use is a servo o-ring from a 700R4 or 4L60E. But the problem with the release on all but one of the 400 brakes is not in the drum or the clutch pack, the problem lies in the passages that they use.

At 0.010" per clutch, you'll have only 0.050" to 0.060" clearance in the direct drum. Now 0.020" per clutch is too loose, at least it is for me. I actually use a 6 clutch pack with about 0.080" clearance. It seems that most often when you exceed 0.080", you end up with a 2-3 shift flair, and the car rocks forward a little when the brake is applied. Now, 0.050" to 0.060" is fine for the forward input drum.

If you go the cheap route, and use standard steels, note there are 2-3 different thickness steels. You can adjust your clearance that way. Also note that some drums cannot be used with shorter pistons, as the steel that sits on the piston can drop too low and rotate, then it will not apply.

I've had a lot better success, and longevity, from the Alto Red Eagle clutches and Kolene steels. My 350, 400 and PowerGlide transmissions go forever between overhauls, with no problems, and even after a couple of seasons or more, they look like new. I use the Alto stuff in every clutch pack.

How you set one up depends on what brake is in it. ATI makes a good budget 400 brake, and the TCI isn't bad. We had trouble out of all of the others. With one exception. The absolute best brake for a 400 is the Griner, even ATI will tell you the Griner is better than theirs.

[Tom Goldman]

X2 on the Griner 400 brake,it's absolutly the best.
Same for the rest of his valve bodies,never had any issues .