a body rearend question

[1968dartman]

I have a question that perhaps someone here can answer. I have an 8 3/4 in my dart with small bolt pattern. I also have an early b body 8 3/4 housing with axles. My question is- how difficult would it be to make the big bolt pattern axles fit my a body housing? Would it be as simple as getting the axles cut and the splines cut longer? This question has been flying around in my head for a while so I thought I would ask . Thanks!

 

[pishta]

Yup, thats all you do. chop and respline. Make sure the B axles are not tapered, ie they are the same thickness where you need to cut and spline. Some have a reduced area that would not be big enough to respline. This reduced area actually gives the axle a little twist like a torsion bar to prevent breaking on a hard shock, straight axles are stronger but are more "brittle" if that makes sense. Lookk at both side by side and make sure the bearing is the same dimension from the hub and then compare cut area to original. should be good to go.

 

[dodgedude]

Just be sure to use the brake backing plates and stuff from the B Body also.

 

[rbdart]

I havent seen any b-body axles those yrs that were not tapered,so more than likely yours are tapered and will not support being resplined,you could possibly find some c-body bbp axles and do that[you would want to get the brakes and backing plates as well to make it work] but in all reality you would be wiser to redrill your axles you already have and they match your housing,bearings,flange etc,and you would retain everything as it is now as in backing plates,brakes etc....last set I had done was about 85 bucs if I recall correctly, the machinists marked and redrilled different bolt pattern then welded up old bolt pattern holes,ground down welds flush and installed news studs[I went to 1/2" studs,held up great behind a 440 4spd dart,have done this multible times and seen it done multible times and never an issue and cheaper than buying new axles,I have since cut down a trk housing and narrowed and backbraced it and purchased alloy axles from Mitchells Differentials and saved 80 bucs going to him directly over moser and others being he made them for alot of different distributors,same axles diff sticker...just my experience

 

[gregpurcell]

The only problem with redrilled axles is that you HAVE to use the A body backing plates and drums. That means that the DRUMs have to be redrilled also and every time you replace the drums you would have to have them redrilled.

You can now get new A Body BBP pattern axles ready to bolt in for $225-$350 from several suppliers. Used ones are even cheaper. I've picked up more than one set at swap meets for less than $100. By the time you cut yours and put new bearings on them and run all over town, used axles may be a better option.

Another option is to use the entire B body rear in your A body. If it's a 65-70 B body it's only about and 1 1/2 -1 3/4 inches wider on each side (the 65-67 is even slightly more narrow)

The A body spring seats are 43 inches center to center and the B body is 44 inches. Some people move the seats in a half inch, I just pull the leaf springs sideways and the rear bolts in place.

The wider rear gives you more space from the drum to the leaf spring, so negative offset wheels work well on that swap.

Whichever way you choose, each has it's advantages and problems.

 

[KosmicKuda]

I doubt your B-body axles can be shortened and re-splined to a-body dimensions. I used to have a list of eligible donor cars and I believe for B-bodies, only a very few years of wagons in the early 70's had enough length.

The typical donor cars are 70's C-bodies and vans and pickup trucks from that era. There is an easy dimension check you can do with a tape measure from the outside surface of the flange to the point where the axle starts to taper to see if it's long enough. But it's been too long and I don't remember the magic number. I took pictures with a tape measure of the before and after shortened axles but I don't have access to them here at work.

I used C-body axles (used for $35/pr) and sent them off to Moser for shortening/re-splining. It was about $100 at the time. Don't quote me but I think the shortened axles were exactly 29" when finished. This was probably 6-7 yrs ago and Moser turned them around in no time, 3-4 days including transit time.

But wait...there's more. You need to get new backing plates, hardware, drums, and shoes that are compatible. There is an offset built into the backing plates that only work with the matching parts. If you have brakes on your b-body axle, that would be a nice matching set. Then you need wheels to match the BBP. I pieced all my junk together from swap meets and Rockauto over a period of a year or so.

I distinctly remember checking before and after measurements using a plumb bob to the floor and the conversion added exactly 3/8" to each side for a total track width increase of 3/4".

 

[rbdart]

Yes I forgot to mention redrilling the drums,which really isnt a big deal...I would say his most economical route without changing the rear end is redrilling of the axles and drums,nothing else changes or finding a set of axles already done....and redrill drums