ID my differential?
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Freshman User
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From: S.E. of Indy
ID my differential?
It's a 71 F100 w 302, 3 speed. the tag on my differential reads: Line 1: WDM AC OJB Line 2: 25 8.7 317A
Can anyone tell me what I have from this? I am guessing it's an open differential and want to shop on line for a positraction diff but would first like to know what my ring gear size is (9" ??) and what the gear ratio is. I can run at 50 to 80 mph and it makes no difference in gas milage; always right around 13 mpg.
BTW, I will be pulling the clutch soon to see if they sold me the right one for the V8; not the 6. Looks like all the support to the bell housing and transmission is solid and based on your feedback, will be trying out a new clutch. This is to solve the reverse gear shake Im having. Thanks for the input.
Mike
Can anyone tell me what I have from this? I am guessing it's an open differential and want to shop on line for a positraction diff but would first like to know what my ring gear size is (9" ??) and what the gear ratio is. I can run at 50 to 80 mph and it makes no difference in gas milage; always right around 13 mpg.
BTW, I will be pulling the clutch soon to see if they sold me the right one for the V8; not the 6. Looks like all the support to the bell housing and transmission is solid and based on your feedback, will be trying out a new clutch. This is to solve the reverse gear shake Im having. Thanks for the input.
Mike
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Posi is GM term so you don't want one of them.
Limited Slip or Traction Lock for Ford
WDM AC OJB (Plant ford engineering info)
2:25 8.7 317A 2.25:1 ratio 8.8 ring gear
317A (plant code)
Must be a car axle.
http://www.ridgenet.net/~biesiade/Fordrears.html
http://www.kevinstang.com/Ninecase.htm
http://www.badshoeproductions.com/rear.html
Limited Slip or Traction Lock for Ford
WDM AC OJB (Plant ford engineering info)
2:25 8.7 317A 2.25:1 ratio 8.8 ring gear
317A (plant code)
Must be a car axle.
http://www.ridgenet.net/~biesiade/Fordrears.html
http://www.kevinstang.com/Ninecase.htm
http://www.badshoeproductions.com/rear.html
Last edited by Mil1ion; Mar 7, 2007 at 10:12 PM.
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From: Madison, SD
It would appear someone may have changed the rear end out, or at least I didn't know that the 8.8's came in a '71???? Maybe Numbers will jump in here and clarify.
By the way, not all of us are quite so word sensitive, Posi-trac to me still covers a Ford, even though it may not be "correct" with the purists. Anyway, found this in Widpedia about positraction:
Factory Names
In the 1950s and 1960s many manufacturers began to apply brand names to their LSD units. The most famous of these was Chevrolet's "Positraction". Since then, Positraction (often shortened to "positrac" or merely "posi") has become a genericized trademark for LSDs.
Other factory names for LSDs include
* Pontiac: Safe-T-Track
* Ford: Equa-Lock and Trac-Lok
* American Motors Corporation: Twin-Grip
* Mopar: Sure Grip
* Ferrari: E-Diff
* Fiat: Viscodrive
* TVR: Hydratrak
By the way, not all of us are quite so word sensitive, Posi-trac to me still covers a Ford, even though it may not be "correct" with the purists. Anyway, found this in Widpedia about positraction:
Factory Names
In the 1950s and 1960s many manufacturers began to apply brand names to their LSD units. The most famous of these was Chevrolet's "Positraction". Since then, Positraction (often shortened to "positrac" or merely "posi") has become a genericized trademark for LSDs.
Other factory names for LSDs include
* Pontiac: Safe-T-Track
* Ford: Equa-Lock and Trac-Lok
* American Motors Corporation: Twin-Grip
* Mopar: Sure Grip
* Ferrari: E-Diff
* Fiat: Viscodrive
* TVR: Hydratrak
Thread Starter
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Freshman User
Joined: Sep 2004
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From: S.E. of Indy
Thanks guys. I'm not too thin skinned. I'm gonna pull the tag off and see if I can read it any better in the garage, but I was pretty sure about the 8.7 (why not 8.8?) however, maybe I'm off a digit somewhere.
If I were to get an entire rearend at a junkyard with LSD, what codes should I look for? I think the WDM refers to open diff; what is it for Ltd. slip or the equa-loc/trac-loc?
If I were to get an entire rearend at a junkyard with LSD, what codes should I look for? I think the WDM refers to open diff; what is it for Ltd. slip or the equa-loc/trac-loc?
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Door tag codes for 9" Locking axles would be:
H2,H4,H6
The codes were explained in the links I made.
Did you not look in them ?
8.7 is an 8 3/4" ring gear.
http://www.kevinstang.com/Ninecase.htm
Could that OJB actually be an "0J8"....? which would mean that axle was cast On September 8th 1970.
H2,H4,H6
The codes were explained in the links I made.
Did you not look in them ?
8.7 is an 8 3/4" ring gear.
http://www.kevinstang.com/Ninecase.htm
Could that OJB actually be an "0J8"....? which would mean that axle was cast On September 8th 1970.
Last edited by Mil1ion; Mar 8, 2007 at 01:23 PM.
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