Axle conversion?

[Madhatter1776]

OK I am totally confused, I have an 8 3/4 axle off of I believe an 68 Dart Swinger, it has the sbp pattern axles, I have measured the backing plate from end to end and it is 11". I want to switch over to the bbp. I have called doc. diff to make sure I get the correct axles, he informed me about the backing plates needing to be switched over. I have been looking for a set of backing plates and after reading I am confused as to what I am looking for. I have read about 10 1/4 10and 2 offset this and that, So if I can get some clarification, with the 11" backing plates I have do I even need to worry about and if so what do I look for? thanks a lot in advance

 

[1968hemidart]

I do these conversions all the time, you want the 11" backing plates and I have a set for sale

MOPAR CHARLIE
727-271-5068

 

[69MOPE]

Or these.
[ame="http://www.ebay.com/itm/8-3-4-Mopar-axles-4-and-4-1-2-bolt-pattern-/291029123410?pt=Motors_Car_Truck_Parts_Accessories&hash=item43c2b00152&vxp=mtr"]8 3 4 Mopar Axles 4 034 and 4 1 2 034 Bolt Pattern | eBay[/ame]

 

[Jimacuda]

Backing plates are larger diameter than the "advertised" brake size. You'll need to measure the inside diameter of the drum, not the outside diameter of the backing plate.
You need 10" large bolt pattern backing plates/drums. They can come from any 1965 and up large bolt pattern rear end. Best to get the complete package so you know they match.
You can also use 11" brakes if you'd like to. I have 11" drums from a 74 Satellite on my Demon. Overkill, but I had them available.

 

[72bluNblu]

You'll want to reference the brakes that you have by the drum size, not the backing plate size. 11" drums use backing plates that are 12 1/8" in diameter, 10" brakes use backing plates that are ~11". Since usually the rear drums are referred to by the drum/shoe size, using the backing plate size gets confusing.

What you need is any 10x2.5" drum brake set up, as the 10x2.5 rear drums only came in BBP. Or an 11x2, 11x2.5, or 11x3" set of 11" drums, all came only with BBP. But with those you have to make sure you get the right shoes and drums, because the backing plates have different offsets for the different width's. Easier to buy a whole set rather than just backing plates, because then you have to figure out what fits, ie, you can't put 11x3" drums and shoes on 11x2.5" backing plates.

Check out this thread too, it shows how to measure the offset to find out if you have BBP or SBP backing plates...

http://www.forabodiesonly.com/mopar/showthread.php?t=258919

As far as these,

Or these.
http://www.ebay.com/itm/8-3-4-Mopar...Parts_Accessories&hash=item43c2b00152&vxp=mtr

I wouldn't touch them. Those are sbp axles that have been drilled to BBP, and you have to use sbp drums that are redrilled as well. Since the SBP drums are getting hard to find, that's not a solution, that's a headache.

If you want to just buy a set of backing plates, take a look at this set of 11x2.5" brakes. I've purchased from this seller before, they have pretty good prices (not much more than the wrecking yard), ship quick and are great to deal with.

[ame="http://www.ebay.com/itm/11-2-5-PLATES-LOADED-MOPAR-DODGE-PLYMOUTH-8-3-4-DRUM-BRAKES-8-75-NEW-YORKER-/281211364925?pt=Motors_Car_Truck_Parts_Accessories&hash=item417980e63d"]http://www.ebay.com/itm/11-2-5-PLATES-LOADED-MOPAR-DODGE-PLYMOUTH-8-3-4-DRUM-BRAKES-8-75-NEW-YORKER-/281211364925?pt=Motors_Car_Truck_Parts_Accessories&hash=item417980e63d[/ame]

 

[Madhatter1776]

Ok, I took off the backing plate today and measured, I do need the bbp set, now I know what I need to be looking for, I will check out that set on ebay you've shown me. Thanks for all the help