Topic: Ring and pinion question

[Groundpounder17]

 Can anyone tell me the difference between the two different 3.91 ring and pinion numbers C8OW-4610-A and C8OZ-4209-A? Both are ford 3.91 ratio but why the different stampings?

[jwc66k]

Can anyone tell me the difference between the two different 3.91 ring and pinion numbers C8OW-4610-A and C8OZ-4209-A? Both are ford 3.91 ratio but why the different stampings?

They may be one in the same. The "W" is a factory part number (aka engineering P/N), the "Z" is a service part number (aka dealer). The service number usually refers back to the factory P/N as the factory P/N has the dimension, tolerances, materials and source. The dual part ID system is a quirk of Ford. GM and Chrysler use a mostly "pure" (non-significant) number system, no decade, no year, no base number (even = RH, odd = LH), no dash number (sometimes). 
Jim

[Groundpounder17]

Thanks, Jim. I would guess that FoMoCo 9 inch ring & pinion sets in 3.91 ratio are the same. Could a difference be the spline count?

[krelboyne]

C8OW-4610-A - I think this is the Ford part number for the pin or pinion alone.
C8OW-4210  from my quick google is the ring gear by itself.

C8OZ-4209-A - Should be the ring and pinion assembly number.

[djjsc]

krelboyne is correct.   I have an NOS C8OZ-4209-A Gearset (3.91 ratio); the crown is stamped C8OW-4210-A (43 teeth), pinion stamped C8OW-4610-A (11 teeth).    A 4th place "Z" in the PN syntax indicates service replacement parts.