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Discussion Starter #1
Have a 74 4 door. And i found the code on rear end but its not lining up with the info ive found.
The code i see is BP O313G2

I got happy when i show the G but im confused about the 2 after. And BP is not a ratio code for my year. So it might be a swap.

Sorry pics are back of the unit. The oil makes my flash go crazy.
Thanks
 

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Mike - 74 Nova Baltimore, MD
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I believe you are correct that the 8.5" rear end that was original installed in your 74 Nova was swapped out for an earlier model 8.2" rear end.
The BP code may indicate a 68-69 2.73 open differential. The "2" at the end of the code may indicate "Night Shift".
https://www.novaresource.org/axle.htm

As shown in the photos below, the 8.5" rear end had two protrusions located at the 5 and 7 o'clock position on the housing.
The 8.2" rear end does not have these protrusions.




Can you tell if there are "C" clips that hold the axles in place within the differential?
If no "C" clips, the rear end was probably from a Buick, Olds, or Pontiac (BOP).
 

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Yeah that is a good possibility. When i got this car the guy told me that they picked it up for the engine and trans. So i guess it was a parts car like most 4 doors. The BP had me really confused... so there is a great chance that my car originally came with 8.5 posi.
 

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Man this is shaking my whole little world right now. When i got the car. I only had 1 bolt holding the sub frame together. And it what missing other little frame nuts and bolts. But the craziest one is that there are 2 set of rear break lines. Now i have to go through this whole car and make sure im not attempting to drive a death trap.
 
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