Are Shims needed: HBW250 Transmission to Bell Housing Flange

[botanybay]

When bolting a Hurth HBW250 to the adapter plate on a Perkins are the 6 bolts sufficient to prevent rotation about the axis of the flywheel or is it necessary to put shims under the washers for the two lower bolts holding the plate to the transmission.

The issue is that while removing the adapter plate from the transmission I discovered two small pieces of metal (which appear to have been under the washers) on the workbench after I took the bell housing adapter off of the transmission. I am not sure where they came from but do not appear to have been just resting in the cavity the transmission makes in the adapter flange as I carried the transmission from where I removed it from the engine and then did not discover the pieces of metal until after I pulled the adapter plate off of the transmission and there were these long thin pieces of soft "pot" aluminum. The thickness of the metal is about the same as the gap between the bell housing adapter and the lower bearing cover which is square.

My theory is that because the transmission can rotate about the axis of the input shaft (the flange is carefully machined to ensure that) a couple of degrees either way that these thin shims were put in to make sure the transmission did not rotate the bearing cover into the bell housing adapter.

If not, then I don't know where these pieces of aluminum came from. They are something like 3/16" x 3/8" x 2" long and have a curve of perhaps of 6" circle. One is long (about 2" and the other is short about 3/4").

The material is beveled on one side and has a somewhat sarated edge like a knife.

Being that I was chasing a noise which I assumed was damper plate springs but with an R&D 7F7 damper plate (linear) there are no springs to end up rattling around in the bell housing.

Anyone have any thoughts.

Sorry for the similar post about torque needs for the 6 bolts.

David

[botanybay]

Interesting thought, the small pieces of material may actually be bits of Zinc rather than aluminum.

David