Rearend ID

[hotrod ford]

Haveing trouble finding info with this 9 inch I have. The truck (1970) it came off of read 3:75. The ID tag says 3:25.
The tag reads as follows:
WDM-S 9K8
3:25 9 313A


Now as for the axle and diff it reads:
C5AW-4668A
DIF 64

Does the tag match the rearend or is this from 64,65 time frame. If so, how do I find the ratio for this rearend?

[Donnie]

If you are pulling it, count the teeth & do the math.
If you are not pulling it
Jack up the rear wheels off the ground
mark both rear wheels at dead center top..i use white out..index with fender well on body
mark the driveshaft yoke to pinion housing with a dot of whiteout, best mark this where it can be easy to see
you need 3 people to read this:
have a person at each rear wheel, both at the same time, make one complete turn of the wheel while a 3rd party watches the driveshaft yoke turn
See how many turns the driveshaft turns to ONE turn of the wheel.....precision counts here if your ratios are close
only 2 persons are needed if your unit has posi, or locked rear.........
ex: if the driveshaft turns 3 & 1/2 times.........you have a 3:50 ring & pinion.......got it???..............Donnie

[hotrod ford]

It's sitting on the garage floor, so I will have to count the teeth.

[BobbyFord]

Try this...> http://www.fordification.com/tech/rearends_ford04.htm