Axle size for 1954 Plymouth Belvedere?

[BobBobLaw]

Does anyone know the axle size for a 1954 Plymouth Belvedere?

I am looking to convert the drum brakes to disc brakes. Of course every website doesn't show a match for my car and when I email them, they ask for the axle size. I think it's an 8.25 but other info online says it may be a 8.75. If there is anyone who has knowledge of this vehicle, I would appreciate the help. (Or maybe just someone to tell me exactly which kit to get?)

I tried to upload pics but just one picture is larger than the 3gb limit.

Thanks

[dpollo]

The axle taper is the same from 37 to 56 although axle lengths and spline counts vary.  The bolt spacing on the backing plate was the same during this era.

 Yours is not an 8 3/4 as that designation referred to the ring gear size which was commonplace in the 60s. It is not really relevant to the brakes.   

[wayfarer]

For the cost of a rear disc brake kit/package I'd venture to say that an Explorer axle would be less money and be a better long-term assembly.  If nothing else, you'll get rid of the tapered axle/stud.

[Frank Elder]

http://www.aajbrakes.com/rearbrakes.html

 

Edited August 5, 2017 by Frank Elder

[Andydodge]

If you have a little bit of mechanical aptitude this may offer a suggestion.........about 35-40 yrs ago I wanted 4 wheel disc brakes on my 1940 Oz Dodge but couldn't find, nor afford the expensive Ford 9" disc brake rear axles that had just been introduced on the Oz Ford Falcons,  so.........

........I installed an Oz 1962 Chrysler rear axle, drum to drum in my Oz 1940 Dodge........I had already adapted disc brakes to the front stubs and wanted discs on the back so I found that Oz late 60's Valiant vented front disc rotors could be removed from their hubs giving me a rotor.......I then removed the rear brake drum from its tapered axle and removed the tapered axle hub from the brake drum..........I then found that the hub fitted inside the Valiant rotor and I was able to use 2 countersunk caps screws to attach the hub to the rotor........................

........I then drilled and pressed Ford F100 wheels studs in from the back thru the hub and disc rotor also increasing the attachment areas of the hub and rotor..........I then removed the stock brake backing plate and cut it down to the width of the outer rear axle seal(like that shown in the pic that Frank Elder's pic shows) and temporarily attached it with 2 of the 3/8th shoulder bolts...........I then installed the hub/rotor back onto the tapered rear axle and temporarily installed the axle centre nut........

.......I then used a vented Ford rear disc caliper and sat it over the disc noting where it cleared the rear spring, shocks and anything else and fabricated a "C" shaped caliper bracket that fitted around the rear axle flange using 4 of the 5 shoulder bolts to attach this bracket.............the 4 bolts that I used were 3/8 UNF cap screws that had to have part of their head ground down to provide clearance on the axle tube to allow the bolts to fit thru the flange, axle shims and seal and the remains of the brake drum backing plate...........

..........dah!!!!.....dah!!!.......a poor mans disc brake rear end which lasted for about 25 yrs until about 15 yrs ago when I replaced it with a 1990's Oz Ford disc brake rear axle.........but that's another story.........

........BUT..........whilst this is an Oz story, the Oz 1962 Chrysler Royal rear axle I used is essentially the same as the 1956 Plymouth, or maybe even the 1953/54 Plymouth as the Oz 1957-62 Chrysler Royal used a 1953/54 body and 313 poly, cast iron auto etc..............

..........so, what I did is essentially what you are trying to do..........check the hub on your rear drums, measure it and look around for a disc rotor that will fit over the hub, then find a rear disc caliper to fit the rotor and away you go...............I don't have any pics apart from these of the car.......which don't really help much......lol............regards, Andy Douglas          

Edited August 6, 2017 by Andydodge
more info

[BobBobLaw]

Thanks for all the info guys.

I know enough about cars to take apart things and put them back together correctly, but I don't know too much about optimizing everything. Would it be best just to replace the axle? Any suggestions on an axle to replace it with? One that I wouldn't have to replace the drivetrain too. I want to restore the car to its original look but I am definitely ok with upgrades that make it perform better and are safer.

[Andydodge]

Bob, what brakes are on the front?.........if discs then it makes sense to replace the rear but as you say it would be easier to just replace the whole rear axle, drum to drum.........here in Oz the Ford Falcons are plentiful and work well but that doesn't help you in the US......I think that a popular swap over there, in the USA is the Ford Explorer or possibly the Dakota rear ends but if you do a thread search the info should come up...........the other thing to keep in mind is that the master cylinder will need to be swapped over to suit the discs tho I'm sure that the disc adaptor companies can help there...........if you still have your stock engine/trans then the parking brake is still on the driveline so it won't need to be connected to the rear brakes unless you want to..........I only went the adapted disc & rotor thing as it was what I could afford back then....the Falcon setup came later and is a much better arrangement all round................anyway I'm sure the other guys on the forum will be able to help............andyd