Author Topic: Will drums off a 7 1/4 fit on 8 3/4 axel & what width shoes? (Read 1877 times)

Sean · « **on:** June 11, 2014 - 09:45:20 AM »

I'm going to be changing out the axel on my 72 Cuda - going from a 7 1/4 to an 8 3/4. Have an 83/4 E Body axel housing without any brakes on it at all. I'd like to use the 10 x 2 1/2 drum off the 7 1/4 and put those on the 8 3/4. I have the bolt pattern for the drum backing plate measured and will have to go to the body shop (he's also painting the rear axel housing as well) to see if the bolt pattern is the same on the 83/4.

Here's the area that I'm a little confused about. How do I find out if I can use the 2 1/2 wide shoes? From what I've researched, there were 3 different widths of shoes that went on Mopars of that era - 2 in, 2 1/2 in & 3 in. I'm guessing shoe width is determined by how far out the axel is from the end of the axel tube. Is this correct?

Last question is, are there different drum backing plates for different widths of shoes?

Thanks!
Sean

Chryco Psycho · « **Reply #1 on:** June 11, 2014 - 11:33:34 AM »

to my knowledge if you use the drum & backing plate from the 7 1/4 it should all work on the 8 3/4 , I believe 3 " shoes were only used on the front , it would be simple to measure form the axle flange to the housing flange & make sure both are the same distance

calicuda70 · « **Reply #2 on:** June 11, 2014 - 11:45:37 AM »

having done that swap on my challenger years yes it will work. think the only thing that didnt fit was the axle vent through the brake line but i cant remember.

Sean · « **Reply #3 on:** June 11, 2014 - 12:12:25 PM »

Thanks for the feedback guys! Looks like it's going to be worth the effort to pull the backing plates off the old axels.

Sean

brads70 · « **Reply #4 on:** June 11, 2014 - 02:30:27 PM »

I agree yep it fits no problem I took the drum set up off the /6 rear end and bolted it right up to the 8 3/4

Sean · « **Reply #5 on:** June 17, 2014 - 07:54:43 PM »

OK, got the backing plates off the 7 1/4. Was pretty straight forward. Take off the 5 bolts and the axle and backing plate come right out. Did have to wrestle with one as the bearing was wanting to stick a little.

A follow up question:

The 7 1/4 axle had 2 1/2 in wide shoes. The on the 7 1/4, the measurement from the flange where the axle mates to the axle housing to the face where the drum sits measures 2 1/2 in.

On my 8 3/4 axle, measurement from the flange where the axle mates to the axle housing to the face where the drum sits measures 2 1/4 in.

That would leave me to believe that I need 2 1/4 in wide shoes. I've never heard of 2 1/4 in wide shoes. I've only heard of 2, 2 1/2 and 3 in wide shoes. Are there such thing as 2 1/4 in wide shoes for our cars or do I go with a 2 in wide shoe?

Thanks!

Sean

brads70 · « **Reply #6 on:** June 17, 2014 - 08:08:50 PM »

I'm not sure about your question but the complete brake assembly from the 7 1/4 rear end bolted right up to the 8 3/4 shoes and all

Sean · « **Reply #7 on:** June 17, 2014 - 08:39:27 PM »

Brad,
Below is a drawing showing the two different measurements. My fear is if I keep the 2 1/2 in wide shoes, they will get sandwiched between the drum and the backing plate. I'm going to have to get the axle back from the body guy to mock it up to see.

Sean

brads70 · « **Reply #8 on:** June 17, 2014 - 08:49:05 PM »

I would say the drum will just "rub" on a different spot?

Sean · « **Reply #9 on:** June 17, 2014 - 09:12:26 PM »

Gotcha! Thanks for the info!!!

Sean

anlauto · « **Reply #10 on:** June 17, 2014 - 09:24:37 PM »

Take all your brakes from your 7 1/4 rear end, including the backing plates, and bolt them to your 8 3/4. You're good to go...

Sean · « **Reply #11 on:** June 17, 2014 - 09:48:57 PM »

Thanks Alan! Just trying to look though the swap and consider any foreseeable issues.

Sean

anlauto · « **Reply #12 on:** June 17, 2014 - 09:54:02 PM »

It's too bad you're not local to me.
I have an E Body 8 3/4 housing, axles, 10" backing plates with brakes listed for sale at $50 and have had no takers...

Can't give this stuff away...

Sean · « **Reply #13 on:** July 05, 2014 - 05:13:41 PM »

Quote from: anlauto on June 17, 2014 - 09:54:02 PM

It's too bad you're not local to me.
I have an E Body 8 3/4 housing, axles, 10" backing plates with brakes listed for sale at $50 and have had no takers... Can't give this stuff away...

Appreciate the offer, Ontario would be a heck of a drive to get it!

Sean