904 rear drum assembly

[MHEAD]

Good morning,
I'm going through my son's 904 trans brake transmission and I'm noticing the spring in the rear drum seems to be chewing up the piston.The pressure plate was also broke between the selective snap ring gap.I had four frictions in it with .042" clearance.
Anyone know what could be causing this?

Thanks

 

[Duster346]

I'd try less clearance in the forward drum--about .015"-.020". No less than that. Any tighter and it may drive forward in neutral. .042" is too much, and "could" have caused the pressure plate to break. You can see it broke right wear the snap ring void is.

The wear on the apply piston from the belleville spring is pretty common in this transmission.

 

[MHEAD]

Well that was kind of my thought also with it cracked there but it's reassuring hearing from you.
I didn't realize how much the piston was wore till I located a spare one.He has about 600 passes on it so I suppose we can't complain much.He's been doubled or running two classes for over year now.
Appreciate your help.