B body rear brakes onto A body axle

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340fourspeedDuster

340fourspeedDuster

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Finally procured the correct rear 8 3/4 A body axle for the Duster. My previous rear axle was a B body 8 3/4 axle with a width of 55" The spring pads on the B body axle are 44" apart. This was run several years with not too many issues. One issue is the A body springs have a 43" spread, leading to rapid bushing wear, and splaying of the leafs.
Redrilled the factory A body axles to 4.5" and installed the 7/16" studs. Problem is the B body 10" backing plates, drums and brake hardware are 2 1/2" wide. This leaves the B body drums sticking out about a quarter inch from the A body axle. When I check the auto parts store, the widest 10" brakes and drum for an A body axle is 2.25". Question is do all brake components have to be replaced, (backing plate, hardware, drums) to get a the drum flush onto the axle? or can I just replace the 10" x 2 1/2" brakes with 10" x 2 1/4" brakes and get the A body drums? Anyone run into this issue?
Thanks in Advance
 
As far as the bridges to have crossed, you should not have an issue since as far as I can tell, all the hardware is the same between the different depths.
 
A-body 8 3/4 axle spacing ,(distance from backing plate to axle flange) is unique and different from all other 8 3/4 rears. To my knowledge there is no way to run the B body plates and drums with your original small bolt A-body axles.
 
I installed 11" brakes from a E body on my Duster with no problem. I used everything from backing plates out.
 
Can't you drill the "A" drums to the larger bolt circle?

What made you go with 7/16" studs?
 
Daves69 said:
Can't you drill the "A" drums to the larger bolt circle?

What made you go with 7/16" studs?
Click to expand...
Yes you could but why when new is at the store?

SGBARRACUDA said:
I doubt with the original A-body 8 3/4 axles? You can buy axles with the correct spacing.
Click to expand...

That's exactly what I did.

If you have the backing plate, you just need to have the correct width brake shoes and correct width drum and your basically good to go. When I ordered my Dr. Diff HD axles, the guy on the phone noted to me the use of B body brakes.

I myself swapped on 11 inch drums.

The current Cuda I'm working on I went with 10X2 with OE axles.
 
I have not purchase drums yet. Trying to keep the snafu's down by learning from those on this board. The original studs were 7/16". When I check the amount of meat left on the flange, going to the 1/2" studs would leave little meat between the original 4" circle stud holes and the new 4.5" circle stud holes.
 
I just stripped a a body 8 1/4 rear with 2.5 shoes. The backing plates were recessed from where they mount to the flange and the drum sat flush against the axel, hope it helps
 
So a 10" x 2" (or 2 1/4" wide) drum for A body rear can be ordered with a 4 1/2" bolt pattern? I will have to do more searching.
 
I just got rid of two sets and they have 5 x 4.5 pattern. One was off a 7 1/4 scamp 1 3/4 the other not sure of but it had 2.45 gears and 2.5 drums.
 
340fourspeedDuster said:
So a 10" x 2" (or 2 1/4" wide) drum for A body rear can be ordered with a 4 1/2" bolt pattern? I will have to do more searching.
Click to expand...


Sorry, my bad, 2-1/2 wide, not 2.

(Now your freak N my head out! Where's my tape measure!)
 
rumblefish360 said:
Yes you could but why when new is at the store?......
Click to expand...

Just pointing out a possible option here.

340fourspeedDuster said:
................. The original studs were 7/16". When I check the amount of meat left on the flange, going to the 1/2" studs would leave little meat between the original 4" circle stud holes and the new 4.5" circle stud holes.
Click to expand...

Using pressed or screw in? 1/2" screw in studs have worked well in mine.
 
A body 8 3/4 with A body axles use A body backing plates the rest of the pieces should work the B body axles stick out farther axle housing flange to axle face than the A body axles do which causes your drum to be spaced away from your axle face. Hope this helps.
 
340fourspeedDuster said:
I have not purchase drums yet. Trying to keep the snafu's down by learning from those on this board. The original studs were 7/16". When I check the amount of meat left on the flange, going to the 1/2" studs would leave little meat between the original 4" circle stud holes and the new 4.5" circle stud holes.
Click to expand...

I don't recommend drilling the axles, but if you must do this, use screw-in wheel studs(bolts)
This will leave a lot more meat in the flange(smaller hole) Maybe enough to use the 1/2" size.

Just noticed Daves'69 said the same thing! agreed
 
Drilling OE A body a les will not solve the problem of the backing plate to axle spacing of the OE axle! Only with an aftermarket axle can you run wider brakes than the OE 1 3/4"!!
 
I have all the hardware from the b-body in my swinger, the fastest way to solve your problem is to buy new axles from Dr. Diff for the 4 1/2 in bolt pattern. The b-body drum will fit good on the new axles, I even took out the b-body emergency cables and put the a-body into the backing plate. No problems
 
cut the spring pads off your B-body 8 3/4, move them to 43" C-C, and put it back in the car.

I don't recommend that anyone use an A-body axle in a Duster/Demon/Dart Sport. Just a bunch of headaches for most of us. I have a 68 b-body axle in mine, and we just put a 1965 B-body axle in my friend's 1971 Demon. Took about 3 hours to move the spring pads on his and we were done. Angle finder, grinder, and a 220V welder is all you need.
 
most of us do not have headaches with A body axles in Dusters and Darts. I think U need the 1973+ A body 4.5" bolt pattern drums, not new axles
 
Wow. Ok,

1. Small bolt pattern axles can only be used with small bolt pattern brakes. That's it. Even if you re-drill the stock axles to BBP, you still have to use SBP backing plates and SBP drums and re-drill them as well. The axle flange offset is unique to the A-body SBP axles, nothing else has that offset.

2. Big bolt pattern brakes can only be used with big bolt pattern axles. That means you can not use big bolt pattern rear drums and backing plates (10x2.5, 11x2, 11x2.5, or 11x3) with ANY stock A-body 8 3/4 axle, as they were all SBP from the factory.

So, if you have 10x2.5" drum brakes and want to use them, you need to buy aftermarket axles and advise the company you plan on using BBP brakes so the axle flange offset is correct for the brakes you intend to use. Call Cass at Dr. Diff, he'll set you straight.

Otherwise, you need to use A-body 10x1.75" brakes (10x2.25" drums are for the front). If you re-drilled the stock axles to BBP you still have to use the SBP brake hardware, you'll just have to re-drill the SBP drums to BBP too. There are no drums you can order that have the 5x4.5" bolt pattern and use SBP axle flange offset.

A-body SBP axles use a different axle flange offset than BBP axles. They can not be interchanged. The BBP axles all used the same flange offset, so you can use BBP brakes off of anything. And the backing plates and drums are NOT interchangeable between the SBP brakes and the BBP brakes. The difference isn't just in the drums, it's also in the backing plates. So, 10x1.75" backing plates can not be used with 10x2.5" drums and shoes or vice versa, the depth of the mounting flange on the backing plate is different. Either re-drill your SBP hardware to match your re-drilled SBP axles, or buy BBP axles to fit your A-body rear axle housing and use the BBP brakes.
 
72bluNblu:
You have the gospel on the A axle. Can this be made a sticky? I have found a source nearby that has the 10" A axle backing plates and drums. The drums have been re-drilled to the BBP. This setup will get the wheels/tires centered in the well.
Thanks everyone for chiming in.
 
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