niel_petersen said:
I suggest one additional decimal point be added to the .pdf inch dimensions to accommodate those of us that still have only inch micrometers.
These numbers are from SKF for a standard application, where we have aluminum hub and housing Maybe we can eventually add some actual readings (including measurement temperatures since we are dealing with aluminum) from the FD rebuild gurus?
Aluminum expands about 11x10^6 microinches/inch per degF.
Hi Niel,
You are still stuck on calling the hub aluminum. I know you corrected yourself before, but you're still stuck on that "brain fart".

Aluminum housing, check.
Aluminum cover, check.
Crowngear assembly tapered roller bearing end- Aluminum, check
Crowngear assembly, crownwheel bearing end (the hub the rear wheel bolts up to) - Carbon steel, not aluminum. This is the trunion that the inner race of the crown wheel bearing is pressed onto.
The interference fit of the inner race of the crownwheel bearing onto this hub is pretty tight. Having pulled off more than 50 of them with a bearing puller, they are on there pretty good.
There was speculation quite some time ago that too tight a fit might be contributing to premature bearing failure by causing bearing impingement. But I think that the looseness of the C3 bearing gives some latitude here. It is the preload on the bearing that is the issue. The more I learn, and the more I think about this, I'm increasingly convinced that it is excess preload shim thickness that is the primary cause of the "classic" crownwheel bearing failure.
Thanks again to you and all those who have contributed to our increasing understanding of the problem. :thumb:
Addendum: as far as getting measurements, I still haven't purchased the needed measuring instruments. The frequency of FD rebuilds in my shop is slowing down, so I'm not sure I'll buy those tools; and I'd have little other use for calipers and micrometers that big. So don't hold your breath.
