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Discussion Starter · #1 ·
I have a 1975 El Camino that came factory with a bop 8.2 10 bolt. It has an open differential with 2.73 gears. I was wanting to put a posi In it. I bought a old rear end with cone style posi with 3.08 gears. Then I changed my mind and wanted to get like a 3.73 gear. I read that the cone may not work with the 3.73. Then I read the entire housing may not work with a 3.73 carrier. Does anyone have any knowledge with how this would work. Thanks.
 

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how did you decide the current rear is a BOP 8.2?
That car would usually come with a 8.5. The 8.5 has a 1 1/4" pinion nut while he 8.2 has a 1 1/8". The 8.5 has 3/4" head LH ring gear bolts while the 8.2 is 9/16 head RH.
You can buy a 3.73 gear set which will work fine in with a 3.07 BOP posi.
 

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The 8.2" BOP was no longer in production after 1972......so how did your 1975 come stock with an 8.2"??

You need to check for sure what you have.....the stock rear should have been the 8.5" corporate 10-bolt.

The only way you have an 8.2" BOP is if someone cobbled it in there.

Differential case series for the 8.5" Corp rear are 2.73-up ('3-series') or 2.56 down( '2-series').

NovaResource - Nova Rear Axle Codes
This will help you identify the 8.5"
 

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Discussion Starter · #4 ·
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This is a picture of the rear end and how I found out it was a 8.2 BOP. I was sure it would be a 8.5 but this says different. So I would be okay getting a 3.73 gear set and put it with the 3.08 cone style posi in the housing that has an open 2.73
 

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The square cornered cast lugs at the 5 o'clock and 7 o'clock locations at the rear cover face indicate it is a 8.5".

I'm with Imsport, I think someone has put a BOP cover on it(who knows why ?!)....gaskets and bolt patterns are the same.

Check the pinion nut size or pull the cover and check it out....BOP ring gear bolts have 9/16" heads, 8.5" Corp have 3/4" bolt heads (and left hand thread, big " L " on the bolt head face).
BOP also has pressed on axle bearings, no C-clips in the center of the differential.

BOP and Corp 8.5" have different case series for gear fit....you need to be sure what you have.
BOP parts won't fit the 8.5", and vice versa
 
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