Denny..the pinion seals appear to have been replaced on the ones I took apart, they must have discarded the felt. I just put my retainer on with RV ( as advised by a few mechanics), I can't see how gasket thickness would be very critical - particularly on the first design of the retainer which fits pretty much flush. It takes a lot of pressure to seat the double race - I pushed mine tight up against the shim with quite a bit of force and I can't see it working loose. I did have to put a speedi sleeve on the yoke. Not an easy job.