4000 S-O-S clutch puzzle

The gap between the pressure plate and the piston measures .790".

The original stack of 5 bronze plates and 5 steel plates measures .647".

The stack of plates with new bronze plates measures .792".

(the original bronze plates measure .060", the new (Ford) plates measure .090".)

The parts guys have no idea what is up with the difference.

Any ideas as to where I should "find" the missing .040"?

Thank you,
Dave

It does have the Direct drive clutch, not the overrunning clutch.

I got new steel plates (C8AP7B442A) that match the original shot ones. The bronze plates (like new condition) I have from the spare transmission. They are thicker, but the pressure plate is thinner so I swapped that too, and everything looks good for clearance, etc.

I had a machinist mig and re-bore the drum that the direct drive clutch assembles in, as the bore had grooves worn into it by the 2 steel seal rings. 5 of 5 of thst part that I have seen had the same wear on them!

Thank you,

Dave

Double check for the correct part numbers. The external splined plates should carry the number PBB77518A, and the internal splined plates should be labled PBB77519A. If that checks out, do you realize that the steel plates are to be dished? Do you realize that these plates must all face the same direction? If not, I suspect that may be where some of the problem lies.

If that's not it, what do your old .060" plates look like? Are they very worn, or do the plates have definite grooves in them like the new ones? It's possible that they are supposed to be around .060" thick, and the new ones you have are mis-packaged (would not be a first for NH!). Also, it's not uncommon to have .100" or more clutch pack clearance in some wet clutch packs. I'm not saying the SOS should be this much (sure would be nice to have some specs for this thing, no?), but clearly there needs to be ample space inside there for those plates to disengage.

Without eyeballing this thing for myself, it would be tough for me to speculate much further. Another option would be to have your dealer call NH and get print specs on both new parts to make sure you do indeed have the right parts.

As far as the confused / .040 part:
At the Ford dealer, by using their computerized parts - pictures - numbers look up program, I ordered 1 bronze plate, due to uncertainty of exactly what the picture showed. (it looked like the whole pack was one part)

Anyways, while looking through the parts at a local used tractor parts place, I found a clutch pack with all of the plates like the one new one I had bought, so I bought all of the used undamaged ones I could find. Also, all of the loose steel plates they had. So far, I have only found steel plates at .068" thick, and they are dished. When stacking them, I checked each to be sure they were going the same way, and the bronze ones in case they had any prefrernce "pressed" into them.

Anyways, the pack I disasembled at the used parts place, had clearance, and the pressure plate was the same thickness as both of mine. I didn't have a way to get the piston out, so I don't know if the piston or the "caseing" piece is different, but something must be. Maybe whoever rebuilt it turned some thickness off of the piston?

The original plates (and those from my spare transmission are .060 thick, and like the new ones, the spline teeth are .034 thick. The bronze "facing" is only about .015 thick on each side, but has a definite, machined (or cast) spiral groove cut into it, with what look like an after thought tic-tac-toe pattern (#) hand ground into them. Imagine the # lines drawn equal to the outer diamiter of the plate, and where they cross the plate is where the ground grooves are. (see image link) The new plates have a much thicker "facing" coating.

The new plates (.090") have radial grooves in the facing. When I dis assembled my #1 clutch, I actually found 4 of the .060" spiral plates and one .090" radial plate. All of the steel plates that worked against the spirals had a spiral wavey wear pattern on them, and the ones that were against the radial plate were just a few thousandths thinner, but nice and flat and even. Clutches #2 and #3 are barely worn. I don't know why this is. The machine had a stop pin in the speed selector that only let it go up to speed 6.

The part number for the .090" plate that I bought is C0NN7B164B. I have no part numbers for the other pieces.

I will take the numbers you gave me and see what the Ford dealer comes up with.

Of all of the "original" spiral .060" plates I have (6 packs worth) none of them measure significantly less than .060". A few look a little "less good" than the majority, so I could pick and choose. For some reason, it seems that the steel plates wear more than the bronze ones. From looking at the wear on other parts, my spare unit had fewer hours on it, but most of the rotating parts were ruined by rust. Oddly enough, the bores for the servos are in much better shape on the spare, so I am going to use it's case for the rebuild.

Thank you again,

Dave

Both of my transmissions have the casting / part number C3NN-7006-B

It might be interesting to see if the upgrade to thicker plates would work. (I know, something else might not fit, making it NG)

Thank you,
Dave

Nice picture. I'm assuming the one on the left is an original. Looks good enough to reuse to me.

It makes sense now, the newer version and all. I did notice many minor variations while looking through all of the parts at the used parts place.

Yes, the plate on the left is the original, and I think I have enough of them in good shape.

Thank you,

Dave