Rear axle swap

[Nomad50]

What rear axle would be the easiest swap into a 1947 Desoto? The posts that I have found are confusing. It seems the best 

ones are '90 thru 2000 Jeep Cherokee, '95 thru 2003 Ford Explorer and '90's Ford ranger. Are the bolt patterns the same, 

and will the driveshaft bolt up? I saw some specs that say all '37 thru '48 MoPar widths are 60" inches. If anyone has done

this some pictures would be nice. Thanks for any help.

[Widowmaker hotrods]

First gen Cameros are 60.5 drum face to drum face. I’ve heard  somewhere that they would work well also.

Edited July 11, 2021 by Widowmaker hotrods
Misspellings

[Sniper]

Camaros have a different wheel bolt pattern

[Andydodge]

In general terms there are no straight bolt in, no modification rear axle swaps......all require some sort of modification or fabrication of something..........as for wheel attachment bolt patterns, the standard mopar pattern was 4.5" same as Ford which they copied from mid 30's mopars.....but even this could be affected by the centre hub/axle diameter...........and then of course there is the driveshaft length and diameter............here in Oz when I built the 40 Dodge in the 1970's I used the Oz 1962 Chrysler Royal rear axle which was basically a 55/56 USA Plymouth rear axle and even then had to redo the spring perches and then in the early 2000's when I installed an early 90's Ford Falcon wagon rear axle whilst it was an almost bolt in regarding the width and spring perch mounts I had to have the mopar sliding yoke driveshaft front installed on the Ford driveshaft which required being done by a local shop..........the only modification to the Ford rear axle assembly was me drilling U bolt holes in a different spot on the Ford spring perch, otherwise it fitted........unfortunately Oz Ford Falcon rear axles would be rather thin on the ground in the USA so all I can suggest is measure what you have then spend some quality time in your local wrecking yard with a tape measure and some sort of wheel bolt spacing tool...................andyd         

[allbizz49]

Regular Cherokee is what I used. Original wheels bolt up, driveshaft doesn't. The original has a ball and trunnion with a 4 bolt flange. Any later rear you use will use a u joint.

[Andydodge]

Sniper is correct.....as far as I know NO GM vehicle of any sort has the same bolt pattern as Ford or Mopars...............most Ford & Mopars use the 4 & 1/2" bolt pattern but some maybe larger......also Ford & Mopars mostly use 1/2" wheel studs whereas GM may use 7/16th.................andyd 

[Nomad50]

So Allbiz, what year Cherokee did you use and was it a 2 or 4wheel unit? And what did you do to solve the the driveshaft problem. 

I presume I will have to use my Desoto spring perches. Thanks for the advice.

[allbizz49]

Mine came out of a 90 2 wheel drive automatic. I bought perches from tractor supply. I haven't driven the car with it yet, still building it but it was an easy swap. If you weld and have basic tools, pretty straightforward. I am installing a t5 as well so it's getting a driveshsft made by a local shop. 

[Nomad50]

Thanks.

 

[Loren]

I am just curious.

Why would someone want to go to the trouble of changing the rear axle?

 

The stock 8.25 axle has a pretty good reputation for durability and it's very easy to change the gear ratio.

The follow on Mopar axle, the 8.75 is the same design just bigger and it has an extremely good reputation.

The Ford 9 inch and the Dana 44 are its only rivals and the Mopar (like the Ford) have pumpkins which make gear ratio changes easy.

The bearings are Timken tapered roller bearings and none of them are proprietary. The seals are readily available and upgradable.

If you want to change the ratio, all you have to do is change the "Pumpkin" and if you get it wrong, you can change it back.

Most of the axles I've heard suggested do not have Pumpkins (like the Dana 44) and you either change the Ring and Pinion under the car or you remove the whole axle to do it on the bench.

It just seems to me to be a lot of work for very little gain.

The last point: would you buy a car with an odd ball rear end? I would not. At least not without following it down the street to see if it "Crabbed".

 

The only two justifications I can see is a gear ratio change and different brakes. The stock rear axle has ratios from 4.3 to 3.54 and brake sizes of 10, 11 and 12 inch. What's not to like about that? Besides 80% of your stopping power is on the front anyway.

Changing the rear axle does not pass my Cost Benefit Ratio (work being a "cost" along with $$).

 

I used to get in arguments with my Dad over "Needs vs Wants" on a regular basis.

He would come up with all these mad scientist ideas on what he wanted. I would listen with polite attention and then tell him he didn't need that stuff to go faster and his money would be better spent elsewhere. He'd get mad as hell but then when he wanted to race...he drove a car I built because his was still on the "drawing board." Just sayn'

[Plymouthy Adams]

ffirst off Loren I am assuming we are going to tailor this thread to the cars of the era represented here on the forum.  With that single viewpoint, ratio.....while changing a pumpkin is easy....finding suitable ratio sets or todays roads is not.....the better gearing has been in the larger Chryslers with larger engine that drove the third member.   Until a source of ring and pinion flood the market...the trend now and in my opinion will continue to be upgrade.   Second and as equally important to many is the brakes.  Later being full floating non interference fit tapered axles and greatly improved provisions for parking brakes.  Third, cost.....one can get a donor rear axle for way often less than the parts to swap a gear out in these older pumpkins should you find one.  I would only consider a pumpkin swap if I got my hands on a nice low mileage original unit and suffer with the brakes as a secondary punishment for being too lazy to swap out for a decent axle.  Actually I have change a number of rear axle and find it not that bad a job but I have never went old school driveshaft and the cost of that upgrade alone is a chunk of money.    Pay to play...yes...do you truly need to play...only the owner can make that call for himself.

[MackTheFinger]

The OP asked a simple question, What rear axle would be the easiest swap into a 1947 Desoto?  and followed with questions about later model rear axles. Not once did they ask about the possibility of swapping gearing in their original differential or the merits of one braking system over another. Just to add to the conversation, other than the necessity of changing driveshafts swapping a "pumpkin" on one of these really isn't much simpler than changing the whole assembly. It is however, easier than arguing with a fence post.

 

[Plymouthy Adams]

as to what is easiest.....I have no clue to the skill of the OP, his tools, work area or if he has access to a wrecking yard....the question put forth here also could be various depending on who did the install and their personal preference.   I guess I was guilty of OT for replying to Loren and his thoughts on axle change.   Personally I think each person needs to do a bit more homework even before coming here and state his need for the upgrade.  Seems he has done some searching....perhaps a visit to the local wrecker for availability of those he has read about will sway him if not by availability, maybe based on price....somewhere you need to get a bit proactive.....many of these swaps will entail driveshaft cost....many will involved braking changes and some may well be axle pattern change or wheel offsets.  Just not many cut and dry answers here on this....I know what I used but my build is so much different than stock and I am assuming he is wanting to keep the engine stock....though none of this is defined by the asker.  We can all assume many things...we can often be wrong doing as such.

[Sniper]

There is something to be said for knowing all your options.

 

Myself, the self adjusting feature of modern drum setups has a lot going for it.  Pretty sure discs on the rear axle of a street car is overkill, at least imo. 

 

But ultimately, my opinion on anything other than my ride is just an opinion, worth what you paid for it.  I have no problems with someone wanting to keep their ride bone stock, period correct or all out hot rod.  I'll help regardless.

[48ply1stcar]

The best things I've done to my 48 Plymouth was last spring when I had a 2000 Cherokee rear axle installed and I installed front disc brakes.  Stopping in a straight line was such a thrill.  The 3.55 rear end with all new brake parts and new drive shaft just gave me a little more confidence on the highway.  I started a thread 5 years before my axle swap to gather information. 

 

[Loren]

Okay so let me recap:

The reason someone would change a rear axle is because it's too much trouble to find a lower numerical ratio?

 

I found 3.54 from a '56 on eBay. I paid $275 delivered. I then took it completely apart, cleaned & painted it and replaced the bearings and seal.

 

Since the parking brake is on the transmission I don't have to engineer a connection to the hand brake.

Since the U joint flange is the same (and in the same place) I don't have to engineer a new drive shaft.

Since the axle housing stays with the car, I don't have to worry about alignment. If the car crabs now (or doesn't) it will (or won't) crab when I am done.

Since the service brakes go back on I don't have to worry about hydraulic compatibility with the rest of the car. If I did change the brakes I would stay with the Mopar type going to 11 or 12 inch drums which use the same hydraulic parts on all the sizes.

Since the axle is basically the same (just a different ratio) I don't have to have different wheels and lug nuts (or bolts) front to rear, not to mention remembering right hand thread, left hand thread front vs rear.

There is a ripple effect. You change one thing and you end up changing everything to accommodate the first change.

 

Seems to me that retaining the original axle and just changing the ratio via the pumpkin is a lot less trouble than changing the entire rear end.

If one does not have the skill/experience to set up the ring & pinion, I would suggest taking it to a 4 wheel drive shop as they setup rear ends all day.

The last place I took a heavy duty truck drive shaft to (to be shortened) could have done it.

 

I was a dealer mechanic for years and I think like one. We don't like to cut and fit. We don't like to re-engineer things. If better parts bolt right on, those are the ones we use. We absolutely hate it when a car comes in and has odd ball stuff on it. None of the bolt sizes are what we expect and the procedures to service/fix it are unknown. It's like asking a surgeon to do veterinary work. A mechanic who works regularly on Plymouths can easily work on DeSotos or Dodge or Chryslers. In my collection of shop manuals I have them all because some times the Plymouth manual doesn't mention something the DeSoto manual does.

It's one of the reasons I like Mopars, "continuity of design".

Don't disturb the continuity! lol

[kencombs]

1 hour ago, Loren said:

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There is a ripple effect. You change one thing and you end up changing everything to accommodate the first change.

 

.

Won't comment on all the other discussion items, but there is much truth this statement.

 

Like my need (want) of an OD.  Not just any OD, I need (want) an A833 from a 79-80 van.  And I really don't know that I will be happy with my six when it's done.  So, I'd like to install an 8 with minimum changes later.

OK, found my 833.  Then found a clutch housing that accepts the large diameter MDG retainer, and bolts to either a 6, early hemi, A or LA engine..  That clutch housing mounts to the frame differently.  So, I bought a matching crossmember and mounts. That housing also has a rt side hyd clutch actuator.  So new firewall mount pedals and masters.   Now no parking brake on the trans.  finally I get to the rear end and my earlier questions.

 

One thing definitely leads to another and another and.......

[allbizz49]

Some of us are hotrodders. i have a bone stock 53 that I drive every day since getting it going. It's staying factory but my 49 is going custom. There are cars that are high quality and put together better than factory that start out as piles of parts. The argument that nobody will buy a modified car isn't true. Resale doesn't matter to me because i will never sale mine so I build what I like. How boring would the world be if someone way back never built an A V8 or if the original Ramchargers (who were Chrysler engineers) never stuffed a 392 into a business coupe? Chrysler was ahead of a lot of people but they weren't perfect. If you don't believe me take a look at your front shock mounts.........

[James_Douglas]

Well,

 

The simplest way is to take it to a rear-end shop and have them take the measurements and order a custom unit from Currie. Full stop, the easy and simple way to go. Just hang on to your wallet!

 

In my case, using a >150 HP engine, I have run my 1947 Desoto in San Francisco city traffic and on the highways at 70 MPH for nearly 20 years. It has 175K miles on it. I changed the rear axle shaft wheel bearings and put in a new pinion seal and that is it. My Suburban weighs more then any of your cars.

 

I have two pumpkins for it. A 4.11 and 3.9. The only failure I had was a ring gear bolt failed and got my attention but even that did not hurt it. I know where there are two more rearends in a yard if for some reason I needed one. (I have a spare housing and axles as well.)

 

Just about all the parts are available if you go looking. At less than 150 HP these rearends just do not break unless something is not looked after. 

 

As to brakes, I came up with a rear disc solution. I have it on the 1949 (see thread on rear disc currently on the forum).

 

I would either stay with the stock unit and just rebuild it or go the currie route.

 

James

 

[Adam H P15 D30]

Going to an 8" Ford rear axle in my 49 gave me:

1. Endless choice of gear ratios

2. No more tapered axles!!!!

3. Much better drum brakes (no special tools needed)

4. Forced me to get rid of the ball and trunion driveshaft for a smoother ride

 

But, I don't leave anything stock so I may be biased?

[Plymouthy Adams]

first off you were fortunate to find the rear axle assembly.....they are not that common for a direct bolt for bolt swap and on the Currie.....if I had to farm it out I'd burn the dang car first......!?

Edited July 12, 2021 by Plymouthy Adams

[Plymouthy Adams]

for many who are not familar....these taper axles are on many cars and not just the old Mopar.....just my inventory.....I have these axles on my Sunbeams Tigers including a third spare 2:88 posi....they are on my Volvo PV544 and both the Jensen Interceptors have these.  My four 1962 Dodge Dart/Polara cars along with the 40's and 50's Mopars about the place....Foreign cars carried these by the name of Salisbury, a European division of Dana...while I do not own a BMW I recall working a couple that were of this nature also...

[Loren]

I did a quick check on eBay.

French Lake has 4 1955 DeSotos.

If they have a Powerflite Automatic (and most of them do) they will have a 3.54 gear ratio.

That's one wrecking yard, one year of one Mopar brand.

Me thinks they are easier to find than most people would believe.

 

And yes I do agree with the sentiment of not farming out a 3rd member overhaul.

We must be in the minority on that however. I went to a large Toyota dealer in Reno, NV asking for bearings for an 2008 FJ Cruiser....even though that axle is weak, they don't stock parts for them. The mechanics change out the whole 3rd member assembly! (at $3,600) Because not one of them is qualified to set one up and they can't be bothered to learn.

 

On special tools: You need a decent hub puller made for the tapered axles and a means to center the brake shoes (the manual calls that a major adjustment). I bought my Ammco 1750 from a guy who charged me what he paid for it, so you can get your money back. The really good hub puller I have was given to me by a friend.

[Plymouthy Adams]

I do not know of a single older Chrysler with a 3:54 sitting around in my area.   I have scoured the woods and the last one I found the other guy found it a couple weeks earlier and snarfed the rear gear.  That has been the only one I could find.....6 years ago at that....and nothing of late has every shown up.   I live in an area where is scrap  metal prices go up...these guy come out of the woodwork for quick easy money and the hobby/cars be danged....they getting their beer money and going fishing.   Can't put it any other way....the truth is the truth.  And we all know the famous line........IF IT WERE ONLY CLOSER............we talking whole cars here that are often a good deal....you think the average joe going to travel for a part.....HARDLY LIKELY.....they sit on couch and hope one will fall in their lap first....I am not pointing fingers folks.....just reading the crime scene....

[Bobb Horn]

On 7/11/2021 at 6:46 PM, Nomad50 said:

What rear axle would be the easiest swap into a 1947 Desoto? The posts that I have found are confusing. It seems the best 

ones are '90 thru 2000 Jeep Cherokee, '95 thru 2003 Ford Explorer and '90's Ford ranger. Are the bolt patterns the same, 

and will the driveshaft bolt up? I saw some specs that say all '37 thru '48 MoPar widths are 60" inches. If anyone has done

this some pictures would be nice. Thanks for any help.

I installed a 1995 Ford Ranger rearend into my 38 Coupe.    The Ranger rear is less in width, so I use spacers to make the rear fit the Coupe.   My Coupe had a 3.9 rear that was too low geared, and the Ranger rear is 3.7 that is better but still to low, and am not a fan of using spacers, so my next step is or was to use the 98 Jeep 3.5 rear, better fit, and not using any spacers

.   The driveshaft I used was from a Explorer 2wd.    My Coupe is a lot smaller/lighter than a 47 Desoto, so like comparing apples and oranges...