8.75 Brake ???

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straightlinespeed

straightlinespeed

Sometimes I pretend to be normal
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Currently my 8.75 has the small bolt pattern, tapered axles. My plan is to buy some LBP axles with green bearings. Figuring I would only have to switch the drums to fit the larger pattern. I was informed I have to switch over the entire brake system with new backing plates, hardware and drums. Is this truely necessary? If that is the case does anyone know what it would take to switch to discs in the rear and how much more to do that? I was quoted about $350 for a drum set up.
 
SMP to LBP rear brakes are a different size. SBP uses a 10 x 1 3/4 shoes & drums & the LBP uses 10 x 2 1/2" brakes & yes they use different backing plates. Just went through all this on a 70 Dart.
 
Why did you change backing plates? If you have 10" backing plates on an 8 3/4, and you buy new LBP axles, you shouldn't have to change backing plates. You can buy axles from Moser for under $300, which are stock A body length, and use your original brake parts. Just redrill the drums for LBP. I did all this on my 70 Dart, no problems.

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Fair enough, but I'm just trying to keep it clear that you don't HAVE to change everything over. It's a lot cheaper to drill your SBP drums to the larger pattern, than to buy everything new.
 
The difference is in the axles!!!!

A body SBP axles use a different offset than LBP axles to run the narrower 10x1-3/4" brakes. So, if your new axles use the original SBP offset, you just need to drill your drums for the larger bolt pattern.

BUT, if your axles use the normal LBP offset, then you MUST use the 10x2.5" backing plates, drums, hardware, etc.

Find out which length/offset your axles have. I believe that Mosers off the shelf stuff is the original A body length and offset, but other manufacturers use the LBP length.

Personally, I would get axles set up with the LBP offset. 10 1-3/4" drums are getting harder to find, and you every time you need new drums they'd have to be drilled for the LBP. If you get axles intended to use 10x2.5" brakes, you just buy off the shelf parts that are easily available.

And I wouldn't buy any of those 10x2.5" brake kits new. The 10x2.5" brakes came on all kinds of Mopars all the way up to the 90's, so they're easy to source at the wrecking yard. Or eBay, they'll cost more than the wrecking yard but should cost a whole lot less than $350.
 
The sb drums will not fit the bb axles and thats a fact. The diameter of the axle is larger so the taper won't fit also the center is larger on the big bolt pattern axle. The backing plates for the BBp is offset farther back allowing the wider brakes the BBp drum will hit the outside of the sb Backing plate. You must use the BBp set up as a whole. Now if you drill your own axles then you can drill the drum. And that is that. So don't listen to anyone that tells you different. I have both setups off and can show you the difference. The outside diameter of the BB axles are wider to accommodate the larger bolt pattern the sb drums do not have a big enough of a flat area to cover the flange. also as stated the sb drum doesn't have a big enough center hub.
 
went you order the axles ...you need to tell them what backing plates you have ...as said..the offset on the axles are different with the LBP vs SBP..

that is why you need to call Doctor Diff went you order axles..
 
Who ever quoted you $350 for a set may have included blasted/cleaned parts with new shoes and hardware but for a good used setup of 10"x2.5"x4.5" lbp, should cost you btween $80-100 /set. Beyond that I would always recommend replacing the shoes and wheel cylinders as you never know how long the brake fluid sat in the lines absorbing water, both are inexpensive enough that you will not break the bank. At the $80-100 range, you should expect used drums that can be turned at least one additional time and your time to clean them up before putting them on.

Next to next to last, if you can only fine 11"x2.5"x4.5" lbp setup, this will work as well but you need to be consious of your rim size as they were typcially on the big C-Body cars that ran 15" rims.

Next to last, the 10"x2.5"x4.5" drums sets were found on many different Mopar cars and trucks well into the eighties, just make sure that when you get a set, it comes with the emergency brake lever and shoe separator bar as the backset of the backing plate is deeper than the 10"x1.75".

Lastly, make sure that the 10"x2.5"x4.5" backing plates have all five mounting holes to the end of the axle tube. Some later model vehicles eliminated the bottom mounting hole because Mopar used only four bolts to hold the plate to the tube 9(typically on trucks) but don't be discouraged, even though they elminated the fifth bolt, most often I have found the fifth hole on housings with only four bolts.
 
I got a complete 11" x 3" brake setup off a B body, called Moser and told them I wanted axles for B body brakes on an A body rear, they sent me exactly what I needed and it's been running for 10 years now.
 
Thank you everyone! I didnt realize all the different options. I have called Cass at Dr. Diff and he is the one that quoted me the $350 for the brake set up. I believe it was everything new. I would rather try to get axle shafts from say a place like Moser and get the correct set up with out swapping the brakes over on top of it. I'll give them a call and get a price through them also. Thank you everyone for the input! Again you all make this site the best!
 
There are several alternatives you may want to consider before making your decision.

According to their web site, Moser charges $370 for a pair of bare axle shafts, plus $65 for bearings and $17 for studs.

If you want to swap over to common 5 x 4 1/2" bolt pattern brakes, my off the shelf A-body 5 x 4 1/2" axle package runs $295 ASSEMBLED. This package results in a 2.5" axle flange stand-out (same as all standard B/C/E body axles).

If you want to use your original A-body backing plates, with an off the shelf (5 x 4 1/2" bolt pattern) 10 x 2 1/2" drum, a pair of my semi custom axles runs $300 ASSEMBLED. This package results in a 2.625" axle flange stand-out.

If you want to re-drill your original brake drums, I can provide a full-blown custom axle package for $400 ASSEMBLED. This package results in a 2.25" axle flange stand-out (same as 5 x 4" bolt pattern axles).
 
Cass,

I'll give you a call when Im a bit closer to ordering these up! I am going to order your axles. I just need to figure out what I want to do.
 
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