REAR DIF Identification

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wescfe
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REAR DIF Identification

Postby wescfe » Mon Nov 06, 2017 1:16 pm

I found a rear end (differential) out of a '74 F-100.
It has a tag, but it's old and rusty.
I request opinion and help with the ID.
I'll attach the picture - here's my interpretation:
WB ? - AC 3LB
? 5 - 9 331A

I can't find a code similar in an the early '70's year range
thanks,
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fastEdsel
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Re: REAR DIF Identification

Postby fastEdsel » Mon Nov 06, 2017 10:55 pm

My guess is it's a Ford 9 inch, 3:31-1 ratio. Poor man's way to try it is to jack up the rear axle off the ground so the wheels spin freely, place a mark on the pinion dust cover, rotate the wheels and see if you get approximately 3 1/3 turns of the pinion to every single rotation of the wheel. Then it's most likely a 3:31 ratio. The only other way is to pull the differential out and read the stamp on the crown gear. Good luck, let us know. :thup:

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basketcase0302
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Re: REAR DIF Identification

Postby basketcase0302 » Wed Nov 08, 2017 8:14 pm

"wescfe"]I found a rear end (differential) out of a '74 F-100.
It has a tag, but it's old and rusty.
I request opinion and help with the ID.
I'll attach the picture - here's my interpretation:
WB ? - AC 3LB
? 5 - 9 331A

I can't find a code similar in an the early '70's year range
thanks,



:wel:
Stop by the welcome mat when you get a chance:
viewforum.php?f=1

What FastEdsel said above will get you close and here's the axle code sheet:

http://www.fordification.com/tech/dana-rear-01.htm
Jeff
viewtopic.php?f=22&t=46251
SOLD-71 F-350 dually flatbed, 302 / .030 over V-8 with a "baby"C-6, B & M truckshifter, Dana70/4.11 ratio, intermittent wipers, tilt steering, full LED lighting on the flat bed, and no stereo yet (this way I can hear the rattles to diagnose)! SOLD!
A lot of "oddball" Ford parts collected from working on them for 34 years now!
2008 Ford Escape 4 x 4

I'm "on the fence" about another bump right now / still looking at them / but not real sure if I'm ready for it or not (until I get moved). :(

ultraranger
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Re: REAR DIF Identification

Postby ultraranger » Sun Nov 12, 2017 3:21 am

Hard to tell for sure from the photo and the amount of crustiness on the tag but, It looks like it reads: WDM-AC

If this is the case, the 3rd member has a 3.25:1 ratio, open (single track) 28-spline differential. "3LB" indicates the 3rd member was assembled the 2nd week of November, 1973.
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.

wescfe
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Re: REAR DIF Identification

Postby wescfe » Mon Nov 20, 2017 3:53 pm

I think UltraRanger is correct - it's the only thing that makes sense.
Thanks everyone for the help.


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