rear drum brakes issue

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the rear has a 2-1/2" brake assembly. backing plates, shoes / hardware, and drums. From reading above, I cannot simply put 1-3/4 shoes on the 2-1/2 backing plates / drums / hardware I have.

is the problem the axles have the incorrect axle offset / brake gap for the 2-1/2 brake package (B-body)? I remember there being two axle offsets. 2.36 and 2.50.
Is the 2.36 for the 1-3/4" brake shoes / A body and the 2.50 for the 2-1/2" brake shoes / B-body

I'm thinking the previous owner ordered axles for a A-body (thinking it was getting A body drum brakes) ........but bought a B body brake assemblies.

or

does it just have incorrect backing plates for the 2-1/2 brake package?

please school me.
 
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in too deep: trying to go BBP on a 68 barracuda and its going.. poorly.

Hi! First off, im new at all this. I wanted a muscle car project, and always loved barracudas. So.. i recently bought a 68 barracuda with a 318/auto thats been sitting for a while. The brakes are a mess, the tires are garbage, and its a 5x4 bolt pattern. I want to drive this thing in...
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The backing plates, the axles, the drums and the shoes and hardware ALL have to match.

You will have to determine what you have.
 
Since the brake assembly is a 2.5" set up there are a couple of possibilities. Since the 10x2.5" drums fit I'm assuming the axles are BBP, 5x4.5"

One possibility is that the aftermarket axles have the original SBP A-body axle flange offset, which is different from the BBP axle flange offset used by every other Mopar. If that's the case, you would need the 10x1.75" SBP A-body brakes with the drums re-drilled for the BBP. Moser still sells brand new A-body axles that have the original SBP axle flange offset, but with the larger bolt pattern, for use with the 10x1.75" set up and re-drilled drums. Totally dumb IMO, but they're out there.

77221140-e312-43b8-bebb-dcc15913be3e-jpeg.jpg


The other is that you actually have BBP axles with the correct offset, but have the wrong backing plates for the 10x2.5" brakes.

To measure the backing plate offset you want to set the backing plate flat on a bench. You'll need to hang the bottom 1/3 of the backing plate off the edge of the bench so that the mounts for the e-brake cables don't keep the backing plate from sitting flat. It isn't much, but they do change the measurement. Then, measure from the bench to the top of the backing plate through the center hole (for the axle) in the backing plate. Since your axle and brakes are all assembled, you might be able to accomplish that measurement using a straight edge across the backside of the backing plate and measuring back into the backing plate where it mounts. The measurement will be smaller, you'll have to add the thickness of the backing plate to match the measurements below.

If you get ~1.75", you have 10x2.5" plates. If you get ~1.25", you have 10x1.75" plates.

img_2848-jpg-1714942228-jpg.jpg
 
72bluNblu said:
Since the brake assembly is a 2.5" set up there are a couple of possibilities. Since the 10x2.5" drums fit I'm assuming the axles are BBP, 5x4.5"

One possibility is that the aftermarket axles have the original SBP A-body axle flange offset, which is different from the BBP axle flange offset used by every other Mopar. If that's the case, you would need the 10x1.75" SBP A-body brakes with the drums re-drilled for the BBP. Moser still sells brand new A-body axles that have the original SBP axle flange offset, but with the larger bolt pattern, for use with the 10x1.75" set up and re-drilled drums. Totally dumb IMO, but they're out there.

View attachment 1716051702

The other is that you actually have BBP axles with the correct offset, but have the wrong backing plates for the 10x2.5" brakes.

To measure the backing plate offset you want to set the backing plate flat on a bench. You'll need to hang the bottom 1/3 of the backing plate off the edge of the bench so that the mounts for the e-brake cables don't keep the backing plate from sitting flat. It isn't much, but they do change the measurement. Then, measure from the bench to the top of the backing plate through the center hole (for the axle) in the backing plate. Since your axle and brakes are all assembled, you might be able to accomplish that measurement using a straight edge across the backside of the backing plate and measuring back into the backing plate where it mounts. The measurement will be smaller, you'll have to add the thickness of the backing plate to match the measurements below.

If you get ~1.75", you have 10x2.5" plates. If you get ~1.25", you have 10x1.75" plates.

View attachment 1716051703
Click to expand...

I like your information and thinking, The backing plates will get the first examination. My gut tells me the rear drum brake assembly (as received) was assembled using the original A-body backing plates.

The incorrect backing plates likely explains why the parking brake adjusters do not line up with slots????.
 
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MoparLeo said:
Hopefully you checked the new parts against the old before you threw the old parts out. If you still have the old parts, just check the shoes and drums against each other.
Click to expand...
You're supposed throw out old parts?
 
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