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    1978 Caprice Coupe rear differential Question

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    sc72buick
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    1978 Caprice Coupe rear differential Question

    Post  sc72buick on Fri Jul 28, 2017 10:00 am

    Hey guys, Im a newb here. I just bought a light green on green Caprice 2 door with 60K miles, original paint car.It still has plastic on the rear seats!!!!. It has been garage kept its whole life. It has not been driven in 2 years due to a faulty master cylinder. In going to service the rear differential, this thing has a BOP 8.2 rear end under it. It has no c clips and no stamp numbers on the axle tube. There is a metal tag that has 2.41 stamped into it, so I know that is the stock ratio. Im 99% sure the diff in the car is original due to the amount of factory coating on it matches the rest of the undersides.
    Question: Is this correct????? Did they use the BOP diff in some of these cars? It is not posi and the car is a 305 2 barrel engine. I have not found anything for sure on the use of these differentials in these cars.

    Cant post pics yet, but will try when Im here long enough, Thanks, Mike Kise

    BrokenBlazerDave
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    Re: 1978 Caprice Coupe rear differential Question

    Post  BrokenBlazerDave on Fri Aug 04, 2017 4:33 pm



    This is the rear axle from a 1979 Chev Caprice 2dr. coupe. It looks just like an 8.2 BOP axle but they went out of production in the early 70's. This axle will fit and interchange most internals with an 8.5 Chev c-clip axle. I have always been told it is an 8.5 BOP axle. If you really have an 8.2 BOP axle the carrier bolts will be right hand thread. All of the 8.5" ring gear axles have left hand threaded bolts holding the ring gear to the carrier. These bolts are usually identified by an "L" on the head. The only downfall with what you have is the carrier will only accommodate a  2.41:1 and a 2.56:1 axle ratio. Anything numerically higher will require a ring gear spacer or a new carrier. The best part is there are millions of vehicle that came with 8.5" 10 bolts with good ratios for cheap. I am also pretty sure the 8.2" axles did not have the ears to the left and right of the bottom 3 diff cover bolts. They were more rounded.
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    Kit1078
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    Re: 1978 Caprice Coupe rear differential Question

    Post  Kit1078 on Mon Aug 07, 2017 9:48 pm

    2.41 was very common on the 77-79, since the cars didn't yet have overdrive they had to do something to make them cruise at highway speeds.

    The cut out cover like that is the "B" or "O" axle, it's an 8.5" full floater. If you want to change the gear ratio to anything higher than a 2.56:1, you need to source a "3 series" carrier. This will allow you to go 2.73:1 and up. The 77-79 uses a 27 spline axle from the factory. Most 8.5" rear ends built before 1987 use the 27 spline, after 1987 they changed over to a 30 spline axle. 1987 are kind of a crap shoot, some are 27 spline, some are 30 spline.

    sc72buick
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    Re: 1978 Caprice Coupe rear differential Question

    Post  sc72buick on Mon Aug 14, 2017 12:09 pm

    Thanks for the info guys. I have been covered up the past few weeks. At least now I know that the rear end is the factory one installed.



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    Kit1078
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    Re: 1978 Caprice Coupe rear differential Question

    Post  Kit1078 on Mon Aug 14, 2017 7:54 pm

    quick way to tell if you have a floating axle: take a rear wheel off and remove the brake drum. If the axle flange (where the studs are) is solid, with no holes in it, then it's a C-clip axle. If the axle flange has three large holes drilled in it, then you have a floater. If i can, I'll try and take a picture of the old axle from my '79, it was a floater.

      Current date/time is Mon Aug 21, 2017 5:30 pm