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Can someone help me decode this differential, it is a 3.25 conventional rear axle according to the Marti report and the tag on it. However I am more interested in which rebuild kit I need to buy in particular to do a complete overhaul or maybe just the seals? Rockauto has a few, so does Dearborn. Anyone have any info to say about the rebuild kits? Any help would be appreciated! Thanks




 

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Discussion Starter #6
well I definately can't reach those bottom bolts with a socket/ratchet, and the rear hump.. makes me think it is a 9". However, the decode says its an 8 3/4". Now I also read somewhere that the 8 3/4" is just a predecessor to the 9" and some just call it that??
Here is the hump and the bolts on the bottom end of the diff:

 

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Hello,

If this helps any, according to "Ford Differentials, how to rebuild the 8.8 and 9 inch" by Joseph Palazzolo, the 8.75" uses a 9" housing, and you can install a regular 9" gear set in it, if you wish to, but otherwise the rest of it is a typical low grade 9", with the non-nodular third member and 28 spline shafts.

DesertXL
 

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Discussion Starter #8
Thanks! Well I am glad I have the beefier 9" housing as opposed to just the 8". Not sure how the 3.25 axle ratio will be with respect to fuel efficiency. I am keeping the 302 all stock so I'd rather have it as fuel efficient as it can be since speed will not be a factor.

Hello,

If this helps any, according to "Ford Differentials, how to rebuild the 8.8 and 9 inch" by Joseph Palazzolo, the 8.75" uses a 9" housing, and you can install a regular 9" gear set in it, if you wish to, but otherwise the rest of it is a typical low grade 9", with the non-nodular third member and 28 spline shafts.

DesertXL
 

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I don't know what you got the housing out of but that is the more desirable tapered housing, maybe alot of Galaxies came out with them but my 64 leaf sprung car didn't. I know the tapered housing came out later
 

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... However I am more interested in which rebuild kit I need to buy in particular to do a complete overhaul or maybe just the seals?
What you are seeing in the RockAuto listings are the differences in:

  • Carrier bearing ID (actual ring gear carrier OD)
  • Gear case bearing OD (same bearing but OD to fit the housing)
  • Choice of pinion bearing crush sleeve or shimmed spacer
  • Pinion bearing size (standard or "Daytona" large bearing for racing)
Unfortunately, this means you generally have to pull the gear case (3rd member/pumpkin/hog's head) out to identify or measure these. You can identify with casting numbers, but the case number is on the inside. The common cases in those years are C7AW, but there are different versions of that number, mostly C7AW-E and C7AW-G. Different bearings. The vast majority use the LM102910/LM102949 bearing set with 28-spline axles, but not all.

The choice of crush sleeve or shimmed spacer is personal in non-critical applications. Both work well in street cars, and it's just the procedure that changes. Most custom diff builders use the solid spacer these days.

I would suggest to pull it for full knowledge, but if that's not possible, the most probable combination is any of the kits with the LM102910, non-Daytona pinion. The choice of crush sleeve or spacer, and bearing brand is up to you.

David
 

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Discussion Starter #11
Thanks David!


What you are seeing in the RockAuto listings are the differences in:

  • Carrier bearing ID (actual ring gear carrier OD)
  • Gear case bearing OD (same bearing but OD to fit the housing)
  • Choice of pinion bearing crush sleeve or shimmed spacer
  • Pinion bearing size (standard or "Daytona" large bearing for racing)
Unfortunately, this means you generally have to pull the gear case (3rd member/pumpkin/hog's head) out to identify or measure these. You can identify with casting numbers, but the case number is on the inside. The common cases in those years are C7AW, but there are different versions of that number, mostly C7AW-E and C7AW-G. Different bearings. The vast majority use the LM102910/LM102949 bearing set with 28-spline axles, but not all.

The choice of crush sleeve or shimmed spacer is personal in non-critical applications. Both work well in street cars, and it's just the procedure that changes. Most custom diff builders use the solid spacer these days.

I would suggest to pull it for full knowledge, but if that's not possible, the most probable combination is any of the kits with the LM102910, non-Daytona pinion. The choice of crush sleeve or spacer, and bearing brand is up to you.

David
 
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