I’ve just been going through the parts manual and I noticed there is two different bearings listed for the front hub on a C15a
C01Q1216 Timken 395s used before serial 184–23657
https://cad.timken.com/item/all-prod...ri-2/395-s-394
And
C11Q1216 Timken 399a used after serial 184–23657
https://cad.timken.com/item/tapered-...ri-2/399a-394a
When I look over the timken data pages there appears to be no difference between the bearings other then the “d-bore” measurement. That difference is 1.588mm with the 395s being the slightly smaller one. My initial thoughts were that the 399a had a higher load rating or something similar.
I’m curious on the change over in with regards to serial numbers. Was that a significant change in production? It may be interesting to see as various hubs could be mixed and matched on trucks today.
