‘67 Disc/Drum - upgrading rear axles to 5x4.5 - any replacement drums?

Brakes for your Classic Mopar

  1. GRANCUDA

    GRANCUDA Well-Known Member

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    I am upgrading my rear axles to some Yukon 5x4.5 units & need some drums to go on. I didn’t know if there were some ‘74 drums I could possibly bolt on or if I should just swap on a disc set-up.

    Anyone just swap some later 9” drums with the 4.5” BC.
     
  2. Jimacuda

    Jimacuda Well-Known Member

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    9" drums on what? Not an 8.75 rear.
    Are the new axles set up with small or large center register?
    Small would be the same as your original A body 8.75 axles...if that's what you have.
    Did you order the axles to be used with your existing brakes?
     
  3. Stephen Mulkey

    Stephen Mulkey FABO Gold Member FABO Gold Member

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  4. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    Small bolt pattern axles (5x4") use a different axle flange offset than big bolt pattern axles (5x4.5"). The difference can bee seen here

    BBP axle shafts copy.jpg

    That difference in flange offset is REALLY important. It means that none of the drum brakes used for SBP axles can be interchanged with the drum brakes used on BBP axles. The backing plates are different, the drums are different- not just the bolt pattern.

    So, if you have your SBP axles re-drilled for the 5x4.5" bolt pattern, you still have to use SBP drums and have them re-drilled as well.

    The problem really comes in with some of the aftermarket axles. Unfortunately, there are aftermarket axles that are made with the 5x4.5" bolt pattern, but the small bolt pattern axle flange offset. Which is terrible, because you can't just look at them and see they've been redrilled. But just like a re-drilled axle, those 5x4.5" bolt pattern axles with the smaller flange offset MUST use SBP brakes with the drums re-drilled for 5x4.5".

    If your new axles are BBP and have the BBP flange offset, then any 10x2.5" drum brake set up will work for you. They came on RWD cars as late as '89, and are pretty easy to find. But you need to use the entire set up, backing plates, shoes, drums, all of it. And those drums are readily available.

    If your new axles are 5x4.5" but have the SBP flange offset, you have to re-use your old backing plates and have the drums re-drilled, and only SBP drums will ever work for you after they've been re-drilled.
     
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    • Stephen Mulkey

      Stephen Mulkey FABO Gold Member FABO Gold Member

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      That's great info. Thanks, I learned my something new for today :)
       
    • GRANCUDA

      GRANCUDA Well-Known Member

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      Thanks for the info, I will measure & see what I have. The new aftermarket axles came with a car I bought, just in the in the trunk in a box.
       
    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      If they're in the box still you may be able to pull the model number and look it up from Yukon
       
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