[Royce P]

I generally use a brass washer instead of the little fiber thingie. The fiber does not last long. Brass lasts a long time and works great. Use a dial indicator on the end of one axle to determine the thickness needed during a rebuild.

I've never found evidence of one upon disassembly of a used T rear end. They just disintegrate.

You can tell it is gone if the axle shaft has in / out play with the wheel removed on the passenger side.