...help with decoding part numbers (9 inch rear)

The 3rd digit of A generally signifies the full size Ford, like a Custom, Galaxie, or LTD. But it's not absolute, as parts that fit multiple vehicles (like axle carriers and housings) just get stamped with an A as a generic Ford code, could have been from a Fairlane or Mustang or a truck, even.

C7 for the housing is '67 and the C6 carrier is a '66. The D2 ring gear is a '72. You probably already knew that, but I'm saying it for other members who don't quite get the Ford part number nomenclature yet.

Count the teeth. If you end up with 39 on the ring and 13 on the pinion, for example, then that's a 3.00:1 ratio. You probably also knew that, too.

That 4th digit of W (or if it was a U, too) denotes axle/driveline. The 4205 and 4210 definitely fall into the "rear axle" range of basic part numbers. I assume 4205 means it's a carrier. I also assume 4210 means it's a ring gear.

I'm putzing around with this page to do this: http://mustangtek.com/FordDecode.html so can't guarantee results. But 4210 is a modern Ford Racing part number when searched on Google. Comes up with Ring/Pinion installation kits on Summit, for example.

The B's after the part number refer to a second revision of the part. Not sure what that may mean, but hey, at least it's not A or unmarked. Parts could have been used any year of or after the code. Could be that all these parts came off a '72 model car for example. The C6-and-C7 coded parts just mean that's the year that part in that casting was designed. Ford would then use them for YEARS if not DECADES afterwards.

Edited by occupant - 11-June-2010 at 2:26AM