8-3/4 Axle question

Engine, Trans & Driveline

  1. Paul Secoy

    Paul Secoy Well-Known Member

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    Hello all, I have a question; I am contemplating using an A body 8-3/4" housing in my 67 Belvedere II, and will have to upgrade to the big bolt pattern axles. I vaguely recall from the last time I bought big bolt pattern axles that they stick out a little further from the axle housing to the wheel flange than the original small bolt axles. Am I remembering correctly, or do I need a nap?.. I am trying to see if this is feasible swap with existing wheels, or will I have to narrow a housing.

    Thanks to all.
     
  2. #41

    #41 Well-Known Member

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    Paul, Tha A-body axle is narrower than the 67 B housing so you will be gaining outer tire clearance and losing inner clearance no matter.
     
  3. cosgig

    cosgig Well-Known Member

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    You’ll have to move the perches as they are different center to center. The aftermarket axles have a different offset to allow you to use B body brakes, although you can buy aftermarket axles with the unique offset needed to run the small bolt brakes if you like.
     
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    • Cranky

      Cranky Banned Staff Member FBBO Gold Member

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      Yup, the stock B axles stick out a bit further than the A body. Can't remember what the figure is but it's out there on the net....
       
    • dvw

      dvw Well-Known Member

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      The B and A are the same housing to flange. The difference is the backing plates. The B uses wider brakes than the A. The B backing plates are deeper. Install B backing plates, shoes, drums and it'll fit.
      Doug
       
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      • Cranky

        Cranky Banned Staff Member FBBO Gold Member

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        I stand corrected....
         
      • Grabbergreendream

        Grabbergreendream Well-Known Member

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      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        You sure? Don't know for a fact but here's a chart about housing widths.https://www.bigblockmopar.nl/tech/mopar-rearaxle-dimensions/ housing.JPG
         
      • Cranky

        Cranky Banned Staff Member FBBO Gold Member

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        Been a long time since having an A body rear end but could have sworn that the distance from the bearing fit to the flange face was different than the B axles.....
         
      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        I'd buy custom axles with b-body bolt pattern. It's like having a narrowed rear. If your car is a 66/67 wheel/tire combos are better. Tire rubbing and wheel BS easier. MO.
         
      • oldkimmer

        oldkimmer FBBO Gold Member FBBO Gold Member

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        If u go on the Doctor Diff site it will explain everything in plain English. Kim
         
      • Cranky

        Cranky Banned Staff Member FBBO Gold Member

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        Who?? JK JK :D
         
      • dvw

        dvw Well-Known Member

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        From the Dr Diff site
        A-body "big bolt pattern conversion axles" fit any '65 and newer, 5 x 4 1/2" Mopar spec rear disc or rear drum brake assembly. These axles will NOT fit 5 x 4" bolt pattern brake assemblies, backing plates or re-drilled drums.

        I just worked on a 67 Cuda that had a locked rear axle. The customer installed 4 1/2" big bolt pattern Yukon conversion axles. He had also installed B body 10" drums. It still had 1 3/4" shoe backing plates. The drum was wedged into the backing plate. I swapped in B Body 10" backing plates and shoes, problem solved.
        Doug
         
      • Dipstick

        Dipstick Well-Known Member

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        The difference in question is the axle flange "standout", the dimension between the axle housing flange and the outside of the axle shaft flange. The SBP A-body dimension is narrower than any other 8 3/4".

        Mopar BBP Ends - 2.525"
        Mopar SBP Ends - 2.22
         
        Last edited: Dec 31, 2019
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        • Fran Blacker

          Fran Blacker FBBO Gold Member FBBO Gold Member

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          I re read post I commented on, you were talking axle to axle flange. I thought it was housing.
           
        • Paul Secoy

          Paul Secoy Well-Known Member

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          Yep, that is what I remembered, and I found it on BigblockDart.com. the big bolt axles stick out 1/4" more per side apparently. I thought I remembered a difference, just couldn't recall the measurement. I'll be using C body backing plates and drums off a parts car I have to save a little cash for this money pit.

          I laid out the axle dimensions at work today with the wheels available to me. I have to try and get a measurement on the car, but if I can get right around 68" sidewall to sidewall, I'll be golden. Thank you very much for the responses.
           
          Last edited: Dec 31, 2019
        • Cranky

          Cranky Banned Staff Member FBBO Gold Member

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          Measure both sides of the car. They are not always the same.....even if never wrecked.
           
        • dvw

          dvw Well-Known Member

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          I stand corrected. Though .250" shouldn't make or brake wheel/tire fit.
          Doug
           
        • Paul Secoy

          Paul Secoy Well-Known Member

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          I will do some measuring, I ran into issues with my 67 Barracuda with body measurements being off a bit. Yes, 1/4" isn't a huge deal, I just couldn't remember how much it was.

          I am hoping I can find a wheel/tire combo that will work without resorting to narrowing a housing. I narrowed one years ago, and it worked out well, but it is a step I would rather skip.

          Thanks again.
           
        • YY1

          YY1 Well-Known Member

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          unless you already have the A body axle, and even if you do...

          66/67 B body housings are WAY easier to find and WAY cheaper.

          A body is typically around $300-$500 without chunk

          66/67 B is typically $100-$200
           
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