Info on 7.25 to 8.75 backing plate swap

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fishman

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I am switching the rear in my 69 cuda from 7.25 to 8.75 whats the best way as far as the brakes go. I have the original ones and also have a set of 11 inch that I was wanting to use but I am using small bolt pattern axels. It looks like that wont work. Any sugestions? Thanks Tom
 
The small bolt pattern axles use their own backing plate, as it sounds like you've already discovered. I'm unaware of any other options except possibly a disc swap of some sort. I can point you to a couple of vendors if interested in discs, but if you want to stick with small bolt pattern and drums, the stock setup is about all I'm aware of.

If you decide to swap in some big-bolt axles, you will have more choices, including the 11" setup you already have.
 
No.

There should be a bunch of the small pattern rear brake setups floating around from people swapping to big bolt pattern. Post a wanted ad and see if anyone has some. Maybe try Moparts, too.

I might have some, but I'd have to go digging, and I'm not sure if I do or not. I know I have one set, but I need it for my wife's car.
 
Yeah, 10.5" rear brakes?

Anyway, those will probably work. Are the brakes from your 7.25 9" or 10"? If 9", I'm not sure how easily you'll find all of the hardware, especially the e-brake stuff. The e-brake cables themselves should work. I had to reuse them myself when I swapped from a 7.25 to an 8.75 and 11" brakes. If it were me, I'd prefer to find an 8.75 setup, complete with drums. Then hopefully you'll have everything you need that you can't easily find at the parts store.
 
Is there a particular reason you want to keep the car small bolt pattern? With big-bolt axles, you'll have more brake and wheel options. Small bolt pattern drums are pretty spendy, unless one of the China companies has started cranking them out. I haven't checked for a few years, but they used to be over 100 bucks each.
 
I thank you Im not sure what to do now. Im shorting a housing I have the axels and a posi center chunk. I would have to get different axels. But then I could use my 11 inch set up
 
Personally, unless you have a specific reason to keep it small bolt, I'd sell the axles and buy some Yukons or something. You could use the rear 11's you have already, and you're have more wheel choices. Of course, you'll want to swap the front to big-bolt discs, but that's easy, too, and you'll end up with better brakes all around. The 11" rear brakes are pretty wide compared to what you've got on the car now. If you're having a custom axle housing made, you might want to consider taking an extra 1/2" off of each end. Of course, you'll want to do some measuring before you do that. It might just help with tire clearance. It all depends on the backspace of the wheel you'll be using. If you haven't chosen the wheels yet, mybe sticking to stock length is best.
 
adriver said:
Or you could use the 7.25 plates on the 8 3/4 with if you were going to BBP axles and the large shoe offset anway.
The bigger brakes MIGHT have a tendency to lock up on you quicker.



http://www.forabodiesonly.com/mopar/showthread.php?t=26201&highlight=brake
Click to expand...

It's been a long time since I looked, but the 7.25 backing plates don't mount to the axle the same way as an 8.75, do they? The 7.25 is a c-clip axle with only four bolts that attach it to the axle housing, and the 8.75" is a semi-floating axle that uses five bolts to hold the backing plate and the bearings in the housing.

I see in that link you posted that he says that a 7.25 setup can be used if it's off of a big bolt pattern 7.25. I think the small pattern cars won't work. I was hoping to do it once, and tthere was no way it would work.
 
Tom, I have a set of 10 inch 8.75 brakes off of my 69 Dart that small bolt pattern. I am going to the large bolt pattern and no longer need these. Would you be willing to trade for the 11 inch brakes? I live just north of Williamsburg in New Kent. Thanks, Matt
 
Matt that might be just the thing that im looking for. This site is great I am glad that I was turned on to this spot. I am at this point wanting to stay with the sbp. I have a complete disc set up off a 67 formula S and am going with ralley wheels. Matt if you want to get together I think that swap would be great. Also need 8.75 shock mounts if anyone might have them. Thanks a lot Tom
 
fishman said:
Also need 8.75 shock mounts if anyone might have them. Thanks a lot Tom
Click to expand...

You can elongate the holes (1/4" on each one) in the 7.25 shock plates to accept the bigger 3" u-bolt. I did that when i swapped from a 7.25 to an 8.25 rear end. It's been about 30k trouble free miles since doing that and 20k have been with a hot 360 that I drive hard.
 
If the 7 1/4 has 10" brakes the brake hardware will bolt right on the A-body 8 3/4 with small bolt pattern axles, it is the same stuff. 7 1/4's are not "C" clip axles, they use a bearing like a "green bearing".


Chuck
 
I believe that in the early 70's they changed to a larger axle bearing that used the axle as a race and went to a c-clip.
 
I haven't found a 7 1/4 yet with "C" clips and I took apart a '75 7 1/4 a couple of weekends ago, but I haven't come close to seeing all of them. There is a different wheel bearing in 7 1/4's but it is between the 9" and 10" brake cars.


Chuck
 
Hmmm... Maybe it was an 8.25 that was in that car. Maybe I should lay off the crack. I need a nap. I could have sworn it was a 7.25. I usually pull 7.25s out and give them away. Most of them have been 9" brake cars anyway. I wonder what's on the rear of the 68 GT. Maybe I should check. If they're 10", I'd better keep the brakes.

Thanks for the info.
 
Definetly keep all of the 10" small bolt brake stuff you can. Any disc brake car (/6 or V8 ) or any V8 car regardless if it is disc or drum will have them.


Chuck
 
Tom,
I will give you call tomorrow evening (Thursday). Just got home from job #1 and heading out the door to job #2. Matt
 
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