7 1/4 to 8 3/4 brake swap

[Sdriche]

I'll be swapping my small rear with 9" brakes to an 8 3/4 with 9 " brakes. The small rear has all new brake parts. Will these easily swap onto the larger rear or are the brakes different? Wasn't sure if 9" was 9" regardless of rear size

 

[dukeboy440]

I'll be swapping my small rear with 9" brakes to an 8 3/4 with 9 " brakes. The small rear has all new brake parts. Will these easily swap onto the larger rear or are the brakes different? Wasn't sure if 9" was 9" regardless of rear size

Not sure you might try cross referencing the part numbers online and seeing that way

 

[burdar]

Some 7-1/4s only have 4 mounting holes in the backing plates where the 8-3/4 has 5. I successfully swapped all the brakes from an 82 Cordoba 7-1/4 to an 8-3/4. I'm not sure what size the rear brakes were on that car. Probably 10".

If your backing plates only have 4 holes then I don't think it's going to work. Post updates when you figure it out one way or the other. I'd like to know too.

 

[krazykuda]

Why not go with 10" brakes on the back of the 8 3/4????

 

[Brooks James]

Why not go with 10" brakes on the back of the 8 3/4????

I will be installing rear discs on my 70 Dart.8 3/4 Which means the backing plates with ebrake cables, complete ,new hardware kit, new shoes, new wheel cylinders. new drums, will be available for sale. It seems you are already in the middle of the swap, These wont be available for at least a month

 

[Dana67Dart]

the center hole on the 7 1/4 backing plate is smaller than on the 8 3/4

 

[Garrett Ellison]

the center hole on the 7 1/4 backing plate is smaller than on the 8 3/4

They are small wheel bolt pattern axles. Also, the backing plate and axle stick out dimensions are different and leave the brake shoes exposed by about a half inch.

 

[Sdriche]

I will be installing rear discs on my 70 Dart.8 3/4 Which means the backing plates with ebrake cables, complete ,new hardware kit, new shoes, new wheel cylinders. new drums, will be available for sale. It seems you are already in the middle of the swap, These wont be available for at least a month

Pm me when you are ready. I only need backing plates but will buy whats available. I'm in no rush

 

[92b]

I'll be swapping my small rear with 9" brakes to an 8 3/4 with 9 " brakes. The small rear has all new brake parts. Will these easily swap onto the larger rear or are the brakes different? Wasn't sure if 9" was 9" regardless of rear size

I don't claim to have this all figured out but I think your backing plate and drum need to match your axle bearing to flange (where the wheel bolts up) offset. I think the offset is narrower on the small bolt pattern(4") and wider on the big bolt pattern (4.5"). You can buy aftermarket big bolt pattern (4.5") axles with with the narrow offset so you will need to measure. Hope this helps and if this is incorrect someone please correct it.

 

[cudamark]

I'll be swapping my small rear with 9" brakes to an 8 3/4 with 9 " brakes. The small rear has all new brake parts. Will these easily swap onto the larger rear or are the brakes different? Wasn't sure if 9" was 9" regardless of rear size

8 3/4 rears never came with 9" brakes, and the ones from a 7 1/4 won't work without major modifications. Also, the A-body version 8 3/4 used 10 X 1 3/4" rear brakes. If you're keeping the small bolt pattern you need to get those particular backing plates along with all the other brake parts for that application.