7 1/4 drums fit on 8 3/4?

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swest

swest

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I have 10 3/4 x 1 3/4 drums on my 7 1/4 small bolt rear, might buy a 8 3/4 but no brakes. (few offers an choices to deal with).

1. will my backing plate fit on the 8 3/4?
2. if not will my guts of the brakes fit on an 8 3/4 backing plate.

brakes are new an would hate to lose out. I have been told that the flared drum shouldnt be on this car, 72 dodge dart swinger 318, 904 police fleet car that they came with different style drums, but the whole car is stock?

thanks
steve
 

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That is the same brake setup that was on the 8 3/4 in the 72 demon parts car I bought.
I think it should swap straight across. I think the key will be to make sure your axles have the correct offset for that size brake.
I swapped all the 10 x 2 1/2 brake parts off my 73 large bolt 7 1/4 onto the 8 3/4 and I just had to make sure the large bolt axles I bought had the correct offset.
The backing plates, retaining pins, and the top bar of the e-brake hardware have to match the drums.
 
I used the backing plates and brake drums off of a 7.25 on my 8.75 and they bolted right up.
Here's a couple of pictures.

74%20dart%20071.jpg


74%20dart%20074.jpg
 
The backing plates will interchange from 7 1/4" axles to 8 3/4" axles, make sure the drum Dia. matches the backing plate dia. (IE: 10'' backing plate = 10" drum). also the bolt pattern is important, depending on year... all 8 3/4 A body axles had a 4" bolt circle and I believe a 10" drum.
The 7 1/4 " was made in many variations.
To answer your question correctly... It depends on many factors.
But in your case, it should all work out.
 
It will work. When I upgraded from a 7 1/4 to my 8 3/4 i swapped the backing plates from the old axle to the new one.
 
Your drums were probably replaced with replacement ones that would fit. after a drum is turned so many times, it becomes weak. Most have a number cast into them that indicates what is the maximum that can be taken off the drum before it should be discarded. Alternitively, one or both of the drums became warped and somebody replaced them. Thats the two most likely situations I can think of
 
Wow so much great information on this site. just started restoring a 72 dart and gonna need all the help i can get.. :) thanks everyone looks like ill get to keep my new brakes.
 
My 70 was ordered by the orig. owner with the HD front end(KH discs and sway bar) which included the flared 10 inch rear drums. They are still with the orig 7 1/4 rearend that was in the car.
 
swest said:
I have been told that the flared drum shouldnt be on this car, 72 dodge dart swinger 318, 904 police fleet car that they came with different style drums, but the whole car is stock?

thanks
steve
Click to expand...

I've got a 72 dart Swinger 318/904 that had 7 1/4 rear with exactly the same drums as in the pic you showed.

The car was a well worn , bone stock , unmolested daily driver survivor from LA so no apparent modifications.
 
greendart72 said:
I used the backing plates and brake drums off of a 7.25 on my 8.75 and they bolted right up.
Here's a couple of pictures.

74%20dart%20071.jpg


74%20dart%20074.jpg
Click to expand...

Is that a Big bolt pattern?
Which axles did you use?
Thanks
 
I see, my came withe same package. so it was an option available at the time. :-D

dustoff440 said:
My 70 was ordered by the orig. owner with the HD front end(KH discs and sway bar) which included the flared 10 inch rear drums. They are still with the orig 7 1/4 rearend that was in the car.
Click to expand...
 
i thought all the 8 3/4s had 5 bolt backing plates. my 72 dart with 71/4 and 10'' brakes are 4 bolt. are the 8 3/4s 4 bolt on a bodies only? dave.
 
i have a 67 C body 8-3/4 i am getting cut down by moser to fit an A body. my parts car is a 74 dart V8 4 door. its 7-1/4 rear has the same mating pattern for the backing plates (5 holes) as the 8-3/4. plus the drums and wheel pattern are the large pattern that A bodys used from 73 to 76

i am planning on using the 74 A body drum setup from the parts car rear on the 8-3/4
 
aaadave said:
i thought all the 8 3/4s had 5 bolt backing plates. my 72 dart with 71/4 and 10'' brakes are 4 bolt. are the 8 3/4s 4 bolt on a bodies only? dave.
Click to expand...
Yup, just going through the conversion now and I see the same. 4 bolt pattern on the 7 1/4 back plates, 5 bolt pattern on the 8 3/4, bummer. Plus the 7 1/4 is a 1.75 inch brake shoe where my new shoes are 2.5 for the 8 3/4. I was hoping to retain the 7 1/4 stuff since its 10 inch, but doesn't seem like an option now.
 
All '65-'89 5 x 4.5" bolt pattern rear drum brakes have 5 mounting holes in the backing plates and will interchange as an assembly, regardless of the application.

5 x 4" bolt pattern 7.25" backing plates will not fit 5 x 4" bolt pattern 8.75" housings, however.
 
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