11" backing plates for A body rear end??

[gt]

11" backing plates for an 8 3/4 rear end is what I want to put on so that we can run the bigger brakes in the A body rear end.
Do the 11" backing plates have to come off an 8 3/4 or are there other rear ends that will have the backing plate that will fit the 8 3/4 (interchangeability).
Any 8 3/4 rear is non existant in my area.

gt

[mopowers]

11" brakes also came on 8 1/4" rears in 70's C-bodies. 

[gt]

Do you know if the backing plates will bolt on to an 8 3/4 rear?

gt

[Jim_Lusk]

They'll all bolt on, but I assume that you've already changed the axles to large bolt with the B/E/C offset on the flange.

[mopowers]

11" backing plates from a 8 1/4" will bolt on to a 8 3/4", but as Jim pointed out, you need to have the "non- A-body" brake offset built into the axles.

In other words, you can't use C body brakes with stock A body axles.

[PureGTS]

You'll have to change the axles to the B/E style axle flange offset. The standard A Body 8 3/4 axles will not work with 11 brakes. See also my posting on the "B body center register size" question and you'll understand why. (too much to retype) Suffice to say the Axle housing flange vs the axle mounting flange has three different depths and the A body is not the same.

[Jim_Lusk]

You change over by replacing the axles, either with cut-down factory axles or with aftermarket axles.

[PureGTS]

  That's the only way.

[69 Dartified]

You'll have to change the axles to the B/E style axle flange offset. The standard A Body 8 3/4 axles will not work with 11 brakes. See also my posting on the "B body center register size" question and you'll understand why. (too much to retype) Suffice to say the Axle housing flange vs the axle mounting flange has three different depths and the A body is not the same.

I recently bought 11" backing plates and drums after I had already purchased A body aftermarket axles (Yukon). So if I am reading this correctly, I will be unable to use them because of the difference in the offset?

[mopowers]

If the Yukon axles were made with an A body brake offset, than you have to use A body brakes with them.

[gt]

Was not aware of this, good info.

gt

[mshred]

You'll have to change the axles to the B/E style axle flange offset. The standard A Body 8 3/4 axles will not work with 11 brakes. See also my posting on the "B body center register size" question and you'll understand why. (too much to retype) Suffice to say the Axle housing flange vs the axle mounting flange has three different depths and the A body is not the same.

I recently bought 11" backing plates and drums after I had already purchased A body aftermarket axles (Yukon). So if I am reading this correctly, I will be unable to use them because of the difference in the offset?

If i am understanding correctly, axle flange offset is determined by which axles you have...B/E style axles have a large bolt pattern and the correct axle flange offset for the backing plates, so if you are running the a-body Yukon axles with the large bolt pattern flange, i would assume that the 11" backing plates will work just fine since it would be just like using B/E body axles modified to fit an a-body

[69 Dartified]

You'll have to change the axles to the B/E style axle flange offset. The standard A Body 8 3/4 axles will not work with 11 brakes. See also my posting on the "B body center register size" question and you'll understand why. (too much to retype) Suffice to say the Axle housing flange vs the axle mounting flange has three different depths and the A body is not the same.

I recently bought 11" backing plates and drums after I had already purchased A body aftermarket axles (Yukon). So if I am reading this correctly, I will be unable to use them because of the difference in the offset?

If i am understanding correctly, axle flange offset is determined by which axles you have...B/E style axles have a large bolt pattern and the correct axle flange offset for the backing plates, so if you are running the a-body Yukon axles with the large bolt pattern flange, i would assume that the 11" backing plates will work just fine since it would be just like using B/E body axles modified to fit an a-body

The axles that I got are the 4.5" pattern and not the 4". So am I OK then or not? If not, then I will just have to find someone to swap them with.
Greg

[mopowers]

Bolt pattern is independent of brake offset.  I'm not sure what brake offset Yukon Axles have.  I assume they will make them based on the info you give them.  That's why axle manufacturers ask what brakes you plan on running.

[mshred]

You'll have to change the axles to the B/E style axle flange offset. The standard A Body 8 3/4 axles will not work with 11 brakes. See also my posting on the "B body center register size" question and you'll understand why. (too much to retype) Suffice to say the Axle housing flange vs the axle mounting flange has three different depths and the A body is not the same.

I recently bought 11" backing plates and drums after I had already purchased A body aftermarket axles (Yukon). So if I am reading this correctly, I will be unable to use them because of the difference in the offset?

If i am understanding correctly, axle flange offset is determined by which axles you have...B/E style axles have a large bolt pattern and the correct axle flange offset for the backing plates, so if you are running the a-body Yukon axles with the large bolt pattern flange, i would assume that the 11" backing plates will work just fine since it would be just like using B/E body axles modified to fit an a-body

The axles that I got are the 4.5" pattern and not the 4". So am I OK then or not? If not, then I will just have to find someone to swap them with.
Greg

Hey Greg,

since the Yukon axles arent custom made, i suggest giving Yukon or the place you purchased the axles from a call and see what they say....oh and do me a favour and post it up if possible because i am planning to go with the a-body Yukon axles with the large bolt pattern and 11 inch backing plates

Matthew

[joesnow]

If you have the Yukon  4 1/2" pattern I would assume you did not redrill the Small bolt drums and have the wide brake shoes. If this is the case you can swap to the  11". Why do you really want them? They cost more for drums, shoes, and cylinders.

[69 Dartified]

If you have the Yukon  4 1/2" pattern I would assume you did not redrill the Small bolt drums and have the wide brake shoes. If this is the case you can swap to the  11". Why do you really want them? They cost more for drums, shoes, and cylinders.

The interesting thing is that I have evrything that I needed, I thought, including brand new finned drums(NOS). The shoes & slave cylinders need replacing but other than that everything else is good.

Matthew,

I got them (Yukon axles set up w/green bearings) from Mancini Racing and they are not the redrilled version but just the 4.5". I will try get a hold of them tomorrow as the time difference has them closed right now. I live on the west coast. If you want to check out their prices and whatnot, just go to ManciniRacing.com

Greg

[mshred]

Hey Greg,

The axles you have are the same ones I am planning to get....I want to run 11 inch backing plates because hey mine as well right? the bigger the better for stopping power...I have checked Mancini's prices but i wasnt clear on it so i was going to call them, although that got sidelined right now...im looking at this seller on ebay who wants $199.99 for them plus 100 bucks shipping to Canada- this is without the green bearings (green bearings are another $90 which i will have to get)...how much did you pay for both axles and the bearings from Mancini's? Hopefully everything works out for you if you already have the backing plates as it would be a shame for them to not work now with the new axles...anyways let me know

Matthew

[69 Dartified]

Hey Greg,

The axles you have are the same ones I am planning to get....I want to run 11 inch backing plates because hey mine as well right? the bigger the better for stopping power...I have checked Mancini's prices but i wasnt clear on it so i was going to call them, although that got sidelined right now...im looking at this seller on ebay who wants $199.99 for them plus 100 bucks shipping to Canada- this is without the green bearings (green bearings are another $90 which i will have to get)...how much did you pay for both axles and the bearings from Mancini's? Hopefully everything works out for you if you already have the backing plates as it would be a shame for them to not work now with the new axles...anyways let me know

Matthew

Hey Matt,

I paid 279.90 + shipping for the complete setup that I mentioned. The only thing that I didn't get were the studs for the them I wish I had but that can be taken care of in the near future. They are basically ready to install as is right now and they come that way so you don't have to have someone else or yourself do it. Also, if I remember right, without the green bearings they were 95.00 a piece.That is one of the reasons I went through Mancini. Also, you can return them within a certain time period with no hassle as long as they haven't been installed or damaged by you. They even give you the paperwork to give your specific reason for returning. The one thing that disappointed me with them is the way that they packed them. They got a little dinged up by the way that UPS handled them but nothing serious, so I kept them.
You mentioned that you were wanting 11" for more braking power, just FYI, the front brakes are the ones that really do most of the heavy work and the rear brakes add their help. I am putting power assisted disc brake conversion. If you haven't already got them, that would be something you might want to consider. Just thought I would throw that in. I had the same idea as you with the 11" brakes but will doing the other as well. I almost bought the ones you mentioned on ebay bought thought that Mancini was the better way to go.

Greg

[mshred]

Hey Greg,

if you paid 279 plus shipping for the axles with the green bearings installed thats an awesome deal...im gonna have to double check mancini's...as for the backing plates, i know that the front is what handles most of the stopping power and i already have a disc conversion for the front ready to go....i just thought why not go a size up in the rear if i can right? let me know when you find out if the 11" backing plates will work with the yukon axles

[69 Dartified]

Hey Matt,

This is what I found in a search on the internet as the guy that I needed to talk to at Mancini was already gone for the day. This info is from mymoparts.com under rearends. I am going to call them again to verify what this says plus what Joe snw said above us. My bolt pattern is the 4.5" so are the drums I have.

A-body 8-3/4" axle shaft swap:
There are several methods to accomplish this. Custom axles such as Strange, Summers, Moser, etc. can be specified with the larger lug pattern for the A-body housing. Longer axles from a larger vehicle may be cut and re-splined to fit the shorter A-body axle. Donors for this operation are C-bodies, D-bodies, trucks and vans with the 8-3/4" axle and 4.5" BC. Moser Engineering can perform the cut and re-spline operation. When selecting a donor axle shaft, look for one that does not taper along its length. Note: A-body 8-3/4" axles were equipped with 10x1-3/4" drum brakes. Replace these with 10x2-1/2" or 11-2-1/2" brakes and associated hardware from the donor vehicle or similar.

Hope this helps a little. I am stiil going to check until I am absolutely sure though.

Greg

[mshred]

so I am taking from what you are saying it is possible to use the 11inch backing plates?

[PureGTS]

  If you have the axles with the green brgs installed they are probably the right ones. Your best bet is to install them and try. Just swing the exhisting brakes and backing plate on one side out of the away (there should be enough line to do this if you lift the line holder up and release the line. You can do this without having to disconnect the line. Now you can temporarily install the new stuff.
  Put chalk lines across the drum lining's contact surface, bolt them on and turn the axles and adjust the brakes to contact the drum. The removed/smudged chalk lines will show where the shoes are hitting. If the drum/axles can't be turned then it is probably hitting the shoes' sides against the inside of the drum. This too will leave a rubbing mark against the inside edge of the drum. The shoes should clean an area of chalk  just shy of the outer edge of the drum. Remember how when the drum is worn out or ground up it is a pain to get off as it has worn a little lip on the edge of the drum making you back off the adjuster? That's shows the drum and shoes are in proper alignment. Not too deep and not deep enough is what we're looking for. I'm betting you'll come out OK. It is either going to be right or wrong, go or no go. Not questionable.
Good luck!