I am currently in a debate and need help finding a resource to resolve the issue. The debate is over whether Mopar ever factory installed large bolt pattern 7.25 rears in post 73 a-bodies.

Can anyone help?

I have one from a 1974 Dart in my "shed" as a "just in case" spare...it came from a 318 powered 4 door equipped with disc brakes...it is a 7.25" rear and has 10" drums on it, and has a very "sluggish" 2.76 ratio...

Your formula will be something like:

1973-1975

9" and 10" drum brakes = SBP front and rear (with the possibility of the rear brakes on the 10" drum fronts being 9" on the rear during certain years).

Front Disc Brakes= LBP rear end...whether 7.25" rear or 8.25" rear...

Starting in Jan. 1976 All A-bodies were to be equipped with Front Disc Brakes Standard Equipment per the factory (so all rears were LBP from that point on....).


Some F#rd guy giving you grief over swapping the wrong Bolt Pattern on your car when the poor 30 year old 7.25" ker-ploded?

-D.Idiot

P.S. Mopar P/N of 7.25" rear end Axle Shafts with LBP are 3507883 for "reference" per page 3-3 in the 1976 Factory Parts Manual...

My '76 Duster had one, and the Feather I stripped did too. Both were disc brake cars.

The LBP axles and brakes will not swap onto a SBP housing, the ends of the axle tubes and the wheel bearings are completely different.

The LBP brakes will bolt on to an 8-3/4 housing though.

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Official Cookie and Mater Tormentor.

I guess it's been answered, but my '73 4 door dart came with LBP 7 1/4 rear end. Factory 318 A/C car with disk brakes. Rearend was a 2.73 open diff. Don't remember the size of the drums on the back... 10"x2" maybe?

Those would be the 10 x 2 1/2 rear drums and they will bolt right onto a 8 3/4.
DD

Doc, they would not bolt on to a factory A-body 8 3/4 since they were all SBP.

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I guess we should clarify. They will bolt to an 8-3/4 housing. You have to get large bolt pattern axles with the proper spacing made for them to work.

'73-'76 A body used 10X2 brakes.

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Official Cookie and Mater Tormentor.

I am under the impression that the backing plates and 10"x2.5" brakes on my bbp 7.25" rear will also bolt right on to a 8.25" A body rear if I ever find one. Everything is new and the back plates blasted and painted so I am hoping to keep them. They have the larger 5 bolt flange like the bigger rears. I have not checked it out but I suspect the 7.25" bbp axle bearing is the same size as the 8.25" axle bearing. So do all the big pattern backing plates interchange?

According to the 1976 Part Catalog, all models with 10" brakes used the same backing plate, as well as the 11" brakes in all said equipped platforms...only the A-body got 9" rear brakes that year...

Which now behooves the question about the bigger cars, knowing some B-bodies might have had 10" rear drums and some might have used 11" rear drums on the same type of axle (like the 8.25"), if someone wanted to stop "really" good and didn't mind the extra weight, can we bolt a set of 11" backing plates and drum brakes to the late 8.25" rear? (It's not really necessary, but it would be nice to know for the "can it be done" pile)

-D.Idiot