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8 3/4 decoding help

Pierce Gwynne

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May 26, 2019
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Fresno CA
Hello, I recently picked up a 73' Road Runner, the guy threw in an 8 3/4 rear end. I was hoping somebody can help decode this one.

image1.jpeg
 
That is the correct center section for a 73. You would want to measure the axle flange to axle flange distance and the center of axle/spring seat to axle/spring seat to see what it fits if a complete rear end. You can look for a small rectangular tag with the gear ratio on one bolt of the center section and round disk on another bolt if it's a limited slip rear end. You can also "count" your gear ratio if the tags are missing. Rotate the center yoke clockwise & count how many turns it takes to rotate the tire/axle one revolution. Your choices are 2.76, 2.94, 3.23 (most common),3.55, 3.91 and 4.10 to one.
 
That is the correct center section for a 73. You would want to measure the axle flange to axle flange distance and the center of axle/spring seat to axle/spring seat to see what it fits if a complete rear end. You can look for a small rectangular tag with the gear ratio on one bolt of the center section and round disk on another bolt if it's a limited slip rear end. You can also "count" your gear ratio if the tags are missing. Rotate the center yoke clockwise & count how many turns it takes to rotate the tire/axle one revolution. Your choices are 2.76, 2.94, 3.23 (most common),3.55, 3.91 and 4.10 to one.

Awesome thank you. I couldn't find a tag or that bolt ill check the gears by hand. this looks like limited slip to me but could use some better knowledge on it.
That is the correct center section for a 73. You would want to measure the axle flange to axle flange distance and the center of axle/spring seat to axle/spring seat to see what it fits if a complete rear end. You can look for a small rectangular tag with the gear ratio on one bolt of the center section and round disk on another bolt if it's a limited slip rear end. You can also "count" your gear ratio if the tags are missing. Rotate the center yoke clockwise & count how many turns it takes to rotate the tire/axle one revolution. Your choices are 2.76, 2.94, 3.23 (most common),3.55, 3.91 and 4.10 to one.
awesome thank you. I didn’t have the tag or couldn’t find the bolt. It looks like it does have limited slip. What do you think?

5A90FA57-5D41-4811-B963-C1F20B585F25.jpeg
 
Being it's out there should be some stamping on the ring gear, telling you the ratio. Looks too be a sure grip to me.
 
Awesome thank you. I couldn't find a tag or that bolt ill check the gears by hand. this looks like limited slip to me but could use some better knowledge on it.

awesome thank you. I didn’t have the tag or couldn’t find the bolt. It looks like it does have limited slip. What do you think?

View attachment 772852
Yes, that is a sure grip and as Jerry mentioned, the exact gear ratio will be stamped into the edge of the round "ring gear". Just spin it around & look for it. It will be stamped with one of the numbers I listed before.
 
It is a sure grip. The housing is dated for late 72 for an early 73 build.....

The sure grip and ring gear will be dated as well.........
 
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