M4A2 Sherman clutch shim question

[Colin Alford]

Information from post-war civilian manuals

[Colin Alford]

There is some discrepancy regarding minimum thickness of clutch driven plate (disk) which would indicate that it should be replaced.

In my prior post I included images from TM 9-1750G (Power plant maintenance) which indicate the plate should be replaced if it is less than .303”

TM 9-745 (M36B2 vehicle maintenance) agrees with the .303” thickness.

TM 9-731B (M4A2 vehicle maintenance) shows .340” as the minimum thickness.

[Malcolm Towrie]

Fantastic info, Colin! Thank you very much.

You’re right, all the info you gave me clearly states that, with the thickness of frictions I have, there should be two 1/32” shims per bolt. That’s what I’ll install. Mind you, I’ll have to make 12 new shims, which will be a pain. Wonder how much laser or water jet cutting costs??

And the Detroit manual gave some interesting info. The shims aren’t to control the diaphragm spring pressure on the pressure plate, as I had assumed, but to keep the release bearing in its working range. I assume that allows the bearing to release enough to allow the spring to apply full pressure and to pull spring back enough to let friction plate spin freely.

Thanks again. I love MLU.
Malcolm

[rob love]

When I google the shim number listed in Colin's part manual, it does come up as a shim for detroit diesel. Might be worth a try asking the local detroit dealer. The number seems to be expanded a little to D81260-755429 SHIM.

[Malcolm Towrie]

Thanks, Rob. Will do.

[Lynn Eades]

It looks to me that the thrust bearing pulls the center of the spring (diaphragm) (away from the flywheel) to release the clutch? The reverse of "normal" If so, then you are still getting full spring pressure, but without the shims, there possibly won't be enough travel at the thrust bearing to properly release.

[Malcolm Towrie]

Originally Posted by Lynn Eades

It looks to me that the thrust bearing pulls the center of the spring (diaphragm) (away from the flywheel) to release the clutch? The reverse of "normal" If so, then you are still getting full spring pressure, but without the shims, there possibly won't be enough travel at the thrust bearing to properly release.

I don’t know, Lynn. When I tighten the bolts clamping the clutch housing above to the flywheel I can feel the torque increasing from the diaphragm spring loading up. If I had 1/16” of shims between housing and flywheel, there would be less compression on the spring when bolts tightened down.
Malcolm