Rear drum question 7.25 vs 8.75

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ragtopfury

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Are A body small bolt pattern 10 inch rear drums interchangeable between a 7.25 and an 8.75 rear. And yes, both rears are original A body rears.
 
Not worried about the plates. They won't change from one rear to the other. Just wondering about the drums, themselves.
 
Gotcha. BluNblu probably knows this.
I do know that backing plates can have different depths. I’d bet, they would swap over just fine but I DON’T KNOW FOR SURE!
 
I'm at a 99.999% yes on the drums being interechargable.

I'll get back to you with the final 0.001% in a few minutes with proof.

There you go, from the handy dandy factory parts book.

Only one drum listed for 10 inch A body Brakes.

Screenshot_20230323-225800.png
 
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I am unsure if any small bolt pattern 7.25 rears came with 10" brakes. Did they?
 
I am unsure if any small bolt pattern 7.25 rears came with 10" brakes. Did they?
Lots and lots of them did, some even with the large bolt pattern.

As for the OP’s question…..yes, the drums are the same. The backing plates however….7 1/4” has only 4 mounting stud holes whereas the 8 3/4” has 5. Yes, you can drill the 5th hole.
 
As for the OP’s question…..yes, the drums are the same. The backing plates however….7 1/4” has only 4 mounting stud holes whereas the 8 3/4” has 5. Yes, you can drill the 5th hole
I believe the bearing hole is smaller on the 7 1/4 also
 
Lots and lots of them did, some even with the large bolt pattern.

As for the OP’s question…..yes, the drums are the same. The backing plates however….7 1/4” has only 4 mounting stud holes whereas the 8 3/4” has 5. Yes, you can drill the 5th hole.
Ok, that's what I was thinking that only the large bolt pattern came with 10" brakes, but I take your word for it. Thanks!
 
I used the entire brake assy of a 7.25 big bolt pattern on my 8.75 with Dr. Diff big bolt axles.
 
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On a 5 bolt pattern, you have to measure from the center of one hole to the outside of an opposite hole, not an adjacent hole.
 
That's because a '73-6 7 1/4" rear end with the big bolt pattern has 10 X 2 1/2" brakes. The earlier small bolt pattern 10" brakes are only 1 3/4" wide, which means they have a different backing plate.
 
Ok, that's what I was thinking that only the large bolt pattern came with 10" brakes, but I take your word for it. Thanks
Do I need to take a photo of my stock SBP 10 inch rear drums on my 7 1/4" for you to believe! :poke: :lol:
 
My drums and brakes swapped over from my 1975 BBP 7.25 to the A Body 8.75 housing (1968). I also used Dr Diff's axles.
 
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