Brake shoes help (8 3/4 BBP)

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Trevor B

Trevor B

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I picked up a donor car: 1964 Dart that had at some point been destined to be a race car: 360, 727, and 8.75 BBP rear end. The rear brakes were in bad shape and I wanted to get them rebuilt (and tested) before pulling the rear and putting it in my 1973 Duster.

But when I tore down the drum brakes and cleaned up, I found that there are significant differences in the backing plates (tabs). Also, the brake shoes on the 8.75 are way skinnier and also shorter than the ones I pulled off my '73 (from 7.25 BBP rear).

So... should I just buy new brake shoes for the 8.75 or should I pull the backing plates off the 8.75 and put the 7.25s on so I can simply re-use all of the brake components (which are in good condition).

Wouldn't I get more stopping power with the larger brake shoes from the '73?

Here's a picture:
8 3:4 brake shoes.png
 
I would pull the axles and change out the backing plates,
 
What size and width are the brakes on each? 9, 10 or 11 in drums? 2, 2.5 etc. width shoes? You dont want too much rear brake or you will be locking them up with the stock proportioning valve. I went with 11x2.5's on my val and it is too much. I added a Wilwood manual prop valve to compensate, but that much brake is unnecessary on my car.
 
Looks as if the brakes are from when it was small bolt pattern, those are 1 3/4" shoes!! What drums is this running?? Redrilled??
 
Better to much and turn them down than not enough if you figure in the heat factor.
 
Unfortunately, I didn't snap enough pictures before leaving the garage for the day.
The drums look the same as my 7.25 rear. The backing plates are definitely different - the tabs are raised higher and don't allow the wider 7.25 shoes to seat properly.

I don't know what the 8.75 came out of but it was fitted with Moser big bolt axles before I got it.

EDIT: I just looked through some documentation and the rear end supposedly came out of a '69 Charger.
 
Okay:
Drums off the 8.75 are 10" inner diameter, as are the 7.25.
Shoes off the 8.75 are 1.75" and the 7.25's are 2.5"

Some FABO reading suggested that the 7.25" backing plates for SBP had only 4 bolts. My 7.25" BBP has 5 bolts.

Seems like I should just pull the axles and change the backing plates, basically using the entire 7.25" setup.
 
Trevor B said:
Okay:
Drums off the 8.75 are 10" inner diameter, as are the 7.25.
Shoes off the 8.75 are 1.75" and the 7.25's are 2.5"

Some FABO reading suggested that the 7.25" backing plates for SBP had only 4 bolts. My 7.25" BBP has 5 bolts.

Seems like I should just pull the axles and change the backing plates, basically using the entire 7.25" setup.
Click to expand...
I think that is the ticket. The 10" x 2.5 would be perfect. The reason the mount pads are different is b/c of the different shoe width. I went through this on mine. Had to buy a set of backing plates with for the right shoe width as the originals weren't right for the brand new drums I had. Anyhow if the backing plates from the 7.25 work on the 8.75 use em'!
 
Uh, nope nope nope.

Moser makes aftermaket axles with the 5x4.5" bolt pattern BUT ALSO with the SBP axle flange offset. If the 8.75 has 10x1.75" brakes on it now, you can't just swap the BBP 10x2.5" brakes and backing plates onto that 8.75", you'd have to swap to BBP axles that have the standard BBP axle flange offset.

You CAN use the 10x2.5" BBP brakes off the 7.25" rear axle though, they are the same as all the other 10x2.5" BBP brakes. But, you can't use them with a SBP axle flange offset.

BBP axle shafts copy.jpg


Maybe the previous owner didn't know the difference between the axle flange offsets and was trying to re-use the SBP brakes with a BBP axle. If that's the case your BBP 10x2.5" brakes will fit the 8 3/4 fine. But like I said, Moser makes axles with the BBP and the SBP axle flange offset, which have to be used with SBP axles and redrilled drums. If that's what you've got, the BBP brakes won't fit.
 
Okay - check it out. I found the receipt from the Moser axles. They appear to be A8000, 30 spline, and listed as "28 4 1/2 Mopar," although I suspect they are actually 27 13/16." Although I can find nothing online to show actual specifications for these axles, I found this FABO ad:

"$900 for A Body 8 3/4 Housing and Axles 5 x 4.50 Bolt Circle with Back Brace, perches set up for Super Stock leaf springs, New Moser A8000 27 13/16 inch axles, New Timken Bearings seals and adjusters, 10 x 2.5 brake backing plates and hardware, and flush mount drain plug."
[SOLD] - MOPAR A Body 8 3/4 Housing and Axles 5 x 4.50 BC with Back Brace and Drain Plug

The bearing package it came with included:
9400M Mopar/Dana/Axle Bearing
  • Bearing OD: 2.875''
  • Bearing ID: 1.562''
https://www.summitracing.com/parts/msr-9400m/applications
and
8002 1/2-20x2" short screw in studs
https://www.summitracing.com/parts/msr-8002

Does any of this information give an answer?

Dumb question: if I pull the axles (that part is easy) and check the fitment of my 7.25 backing plate and it does NOT work, can I put the axles right back again or do I need to get replacement seals or parts in order to do it right? Or, I guess I'd have to put them back if it DID work as well!
 
You should be able to pull the axles and reinstall them without changing the seals. That's not to say that you can't damage the seals when you pull the axles, but if everything goes smoothly it should be fine.

I think A8000 is just the blank for the axle. It specifies the material, not the dimensions which are machined to order. The 9400M bearing is a green bearing set up. The green bearings don't use a thrust block set up like the stock tapered bearings do, so, the axles can be longer. Moser lists all the A-body axles on their website as 28". Moser also sells those axles in 3 variations- for A-body brakes (SBP and SBP flange offset), A-body brakes with re-drilled drums (BBP and SBP axle flange offset) and for BBP brakes (BBP and BBP axle flange offset).

So, all I can tell you is only one set of the brakes you have will actually fit. If the brakes on the 8 3/4 were 10x1.75", the drums fit and no weird spacers were used anywhere, you have a SBP axle flange offset. If that's true, the BBP brakes off the 7.25" won't fit. Is there a part number on that receipt? Should look like A30-CST-A4 (or A30-CST-A45, or A30-CST-AB45).
 
72bluNblu said:
You should be able to pull the axles and reinstall them without changing the seals. That's not to say that you can't damage the seals when you pull the axles, but if everything goes smoothly it should be fine.

I think A8000 is just the blank for the axle. It specifies the material, not the dimensions which are machined to order. The 9400M bearing is a green bearing set up. The green bearings don't use a thrust block set up like the stock tapered bearings do, so, the axles can be longer. Moser lists all the A-body axles on their website as 28". Moser also sells those axles in 3 variations- for A-body brakes (SBP and SBP flange offset), A-body brakes with re-drilled drums (BBP and SBP axle flange offset) and for BBP brakes (BBP and BBP axle flange offset).

So, all I can tell you is only one set of the brakes you have will actually fit. If the brakes on the 8 3/4 were 10x1.75", the drums fit and no weird spacers were used anywhere, you have a SBP axle flange offset. If that's true, the BBP brakes off the 7.25" won't fit. Is there a part number on that receipt? Should look like A30-CST-A4 (or A30-CST-A45, or A30-CST-AB45).
Click to expand...

Nope, no other information on the receipt.

Any tips to axle removal to do my best to insure no seal damage? These were put in in 2003, in case it matters.
 
The green bearings you have are sealed bearings. There's no separate rubber seal like the tapered bearings have. The only other "seal" should be a paper gasket behind the axle retainer plate, so just be careful removing that. But it's only a paper gasket anyway, is just slides over the bearings so if you do damage it you don't have to pull the bearings or anything to replace it.
 
72bluNblu said:
Uh, nope nope nope.

Moser makes aftermaket axles with the 5x4.5" bolt pattern BUT ALSO with the SBP axle flange offset. If the 8.75 has 10x1.75" brakes on it now, you can't just swap the BBP 10x2.5" brakes and backing plates onto that 8.75", you'd have to swap to BBP axles that have the standard BBP axle flange offset.

You CAN use the 10x2.5" BBP brakes off the 7.25" rear axle though, they are the same as all the other 10x2.5" BBP brakes. But, you can't use them with a SBP axle flange offset.

View attachment 1715036149

Maybe the previous owner didn't know the difference between the axle flange offsets and was trying to re-use the SBP brakes with a BBP axle. If that's the case your BBP 10x2.5" brakes will fit the 8 3/4 fine. But like I said, Moser makes axles with the BBP and the SBP axle flange offset, which have to be used with SBP axles and redrilled drums. If that's what you've got, the BBP brakes won't fit.
Click to expand...
Ha! Who knew? Yeah that would cause some brake fitment probs wouldn't it!
 
What's missing is the pic of the drums You took off of the 8.75, are they are re-drilled SBP units?
 
The drums from the 8.75 look measure identical to the ones from my 7.25
 
Trevor B said:
The drums from the 8.75 look measure identical to the ones from my 7.25
Click to expand...

Measure the depth of the drums from the 8.75 and the 7.25. Did the drums from the 8.75 actually fit? I mean, do they mount up on the axle flange without spacers and without hitting the backing plates? Because if the backing plates and shoes are 10x1.75", the drums for those brakes are not the same depth as the BBP 10x2.5" drums. Is there more than one set of bolt holes drilled in the 8.75" drums?

I suppose the other possibility is that the 8 3/4 axles are in fact BBP with a BBP axle flange offset and someone put the SBP 10x1.75" backing plates and shoes back on there, but with a set of BBP 10x2.5" drums. Obviously you can't use the BBP drums with a SBP axle flange offset, the drum hits the backing plate because the axle flange isn't out far enough. But, I don't know how it would line up if you used a BBP axle flange offset with the SBP backing plate and a BBP drum. Obviously you'd have a lot of unused drum surface, even if nothing interfered, because you'd have a 1.75" wide shoe riding around in a drum wide enough for a 2.5" wide shoe.

That would actually be a decent scenario for you though if that's the case, because if that's what happened you could just install the BBP 10x2.5" backing plates and you'd be ready to go. One of the set ups you have either doesn't or won't fit, it's just a matter of which one is wrong. The SBP ones that are on there now, or the BBP ones you want to use.
 
72bluNblu said:
Measure the depth of the drums from the 8.75 and the 7.25. Did the drums from the 8.75 actually fit? I mean, do they mount up on the axle flange without spacers and without hitting the backing plates? Because if the backing plates and shoes are 10x1.75", the drums for those brakes are not the same depth as the BBP 10x2.5" drums. Is there more than one set of bolt holes drilled in the 8.75" drums?

I suppose the other possibility is that the 8 3/4 axles are in fact BBP with a BBP axle flange offset and someone put the SBP 10x1.75" backing plates and shoes back on there, but with a set of BBP 10x2.5" drums. Obviously you can't use the BBP drums with a SBP axle flange offset, the drum hits the backing plate because the axle flange isn't out far enough. But, I don't know how it would line up if you used a BBP axle flange offset with the SBP backing plate and a BBP drum. Obviously you'd have a lot of unused drum surface, even if nothing interfered, because you'd have a 1.75" wide shoe riding around in a drum wide enough for a 2.5" wide shoe.

That would actually be a decent scenario for you though if that's the case, because if that's what happened you could just install the BBP 10x2.5" backing plates and you'd be ready to go. One of the set ups you have either doesn't or won't fit, it's just a matter of which one is wrong. The SBP ones that are on there now, or the BBP ones you want to use.
Click to expand...

Did they fit? I don't know that I can answer that. They were on there alright, but I was a bit shocked to see mag lugs holding the non-mag wheels on there. The car is a bit of a mess, although the body parts look pretty good! Lots of black widows under there made the trip with the car, by the way!

And yeah... a TON of unused drum surface. Those shoes are cracked and all beat up. And covered with some sort of weird reddish orange rubbery substance (not the actual braking surface but everything else).

Will definitely check again but I measured the depth and width of both my old 7.25 drums and the 8.75 drums and came up with the same numbers everywhere. The bolt pattern for the 8.75 drums is LBP and all holes are round and normal looking (no obvious evidence of drilling). I was happy about this as my old drums are in better shape than the 8.75's and figured I'd use them.

One thing I forgot to mention: the car was sold to me "with brake problems." I assumed the seller (whose dad handled the deal but no idea how much either one of them understood what they were doing) didn't know all the details. I thought the leaking wheel cylinders were the culprits but perhaps the whole thing was screwed up from the beginning with all the mixed up parts. I don't think the car was moved for like 10 years. But I still managed to fire her up and drive her onto a trailer... at least the front brakes were working okay and stopped the car.

I will say that I had to back the star wheel off a LOT to get those drums off.

I'm just going to try to find a moment this weekend to pull out one axle and try my 7.25 backing plate on there.

72bluNblu - it's a shame you're not slightly closer (I'm down in Novato). I have a feeling you'd get a kick out of this car. Also, your Demon build has been a great source of inspiration for my work on my Duster.
 
From the first picture it appears you have large bolt pattern axles with the larger center register.
I'm gonna guess whoever did the axle swap just reused the old brake backing plates even though the axles were made for the non A body 8.75 rear plates.
The larger center register forces the use of pretty much any post 65 drum except a stock one from a 72-older A body.
If thats the case you should be able to swap over the brakes, as a unit, from the large bolt 7.25 to your 8.75.
 
Ignorant question: are there c-clips in an 8.75 rear Suregrip? On my 7.25 open, the axles just slid out. These are being held in place by something I can't see. Never had or worked on an 8.75 rear before..

Thanks!
 
Trevor B said:
Ignorant question: are there c-clips in an 8.75 rear Suregrip? On my 7.25 open, the axles just slid out. These are being held in place by something I can't see. Never had or worked on an 8.75 rear before..

Thanks!
Click to expand...

Nope, no c-clips. Once you remove the retainer plates the axles are only held in by the bearings. It should be a tight slip fit. They won't fall out, but you don't usually need a puller of any kind. Couple taps with a dead blow hammer or rubber mallet on the back of the axle flange should take care of it.
 
Done! Axles came out when I used the brake drums as a slide hammer.
The 7.25 backing plates, brake shoes, and hardware all fit just fine.
This rear end is going to be great on the Duster.
Thanks for all the help!
 
Trevor B said:
Done! Axles came out when I used the brake drums as a slide hammer.
The 7.25 backing plates, brake shoes, and hardware all fit just fine.
This rear end is going to be great on the Duster.
Thanks for all the help!
Click to expand...

Awesome!

Guess previous owner tried to use the leftover SBP backing plates with the new BBP axles. Easy solution for you though with the BBP brakes! :thumbsup:
 
I used the 10x2.50 BBP rear brakes from the backing plate out from a 74 dart parts car 7.25 rear on my 8.75 axle. I used 10x2.50 finned drums off the back of a 79 cordoba 8.25. Kept the smooth 74 dart rear drums as spares.
 
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