Rear end swap for bigger engine in future 1948 Dodge custom D24 I believe.

[BayArea48Deluxe]

I am going to want to put in a bigger motif at some point.. so I’m thinking will I have to swap the rear to handle that. I’m thinking either 318 or maybe 360 but I want to know how to figure what would work to fit for a swap. Or would I just need diff?

[Loren]

It’s just my humble opinion and you know what that is worth since you pay nothing for it but….

As a long time racer money was always tight. You don’t change anything until it proves it can’t do the job. If you need a different gear ratio, there are many to choose from. The stock axle is really pretty good and the next MoPar axle is highly regarded for strength and it is the very same design with a half inch bigger ring gear. The stock axle uses Timkin tapered roller bearings that are standard over the counter stuff. Nothing proprietary that you can’t buy every where. 
So save your money there’s other things to spend it on.

If I haven’t convinced you, take a look at the MoPar 8 3/4 axle, they are very good and highly prized. They have lots of ratios, limited slip differentials and they don’t have the drag of a Ford 9 inch and they do have a removable pumpkin.

[QEC]

If your plans include a post-64 trans you will lose the parking brake. Yes, it is possible to change out the old backing plates and such and use later parts to gain the p-brake but an Explorer or Cherokee rear axle is fairly easy to install. Either swap now or when you do the LA but at least start looking.

[Los_Control]

The older jeep cherokee or Ford explorer work fine for the swap.

I mean older in order to get drum brakes .... or newer if you want rear disk.

They do have the same wheel bolt pattern so you can use your stock wheels

 

Seems the modifications would be to remove existing spring perches and weld on new ones .... and install new U-bolts.

The rear yoke will be different and will need to get a drive line modified to fit the modern u-joints.

 

If you do not need to stay original, I'm a firm believer in a rear end upgrade.

The gears will be quieter.

The original brakes are a nightmare to adjust and maintain .... the quality of replacement parts is crap ... brake drum availability is questionable.

 

You need a special puller and a free afternoon just to remove the rear drums from the tapered axle.

They have a woodruff key to hold the axles in place .... you could borrow one from your 3.5 HP Briggs & Stratton lawn mower engine if needed.

Any real power from a engine will shear the keys off and leave you stranded.

 

The ball and trunion u-joints are a nightmare to maintain or find for replacement.

Your original E-brake is almost worthless and attached to the end of the transmission .... A modern rear end has it on the rear axle where it actually works.

 

All I'm saying, for the cost or effort of doing the rear end swap .... You avoid sooo many headaches and expensive repairs.

Pay one time and get self adjusting brakes easily bought at local outlets, A strong rear end that will hold up to some real HP.

Get rid of the goofy ball & trunion u-joints.

 

I'm only sad because my rear end is in perfect condition and needs no work done to it .... if it does in the future, I will replace quicker then a New York minute.

[BayArea48Deluxe]

Thanks. yea I was gonna swap to disk brakes as the next goal. Don’t want drum, they work and all but I think I want more modern so will look into that. So yes getting disk is something I wanted anyways.. and in terms of rear axle change thanks for giving me that info so I can now go do some honing research on what I will need to do.. including to mount either a 318 or 360 along with tranny mounts 

[Dave72dt]

If swapping to a disk brake rear, you probably want to do a front disc conversion at the same time or if doing modifications as a series of smaller, focused projects, prior to the rear disk swap.

[BayArea48Deluxe]

Yes I was looking at front conversion as well sir yes 

[BayArea48Deluxe]

Any place to look that lets me know what parts are doable for my swap? 

Edited November 25 by BayArea48Deluxe

[kencombs]

On 11/23/2024 at 6:32 PM, Los_Control said:

 

 

 

You need a special puller and a free afternoon just to remove the rear drums from the tapered axle.

They have a woodruff key to hold the axles in place .... you could borrow one from your 3.5 HP Briggs & Stratton lawn mower engine if needed.

Any real power from a engine will shear the keys off and leave you stranded.

 

 

I really need to mention this, don't be afraid of rear end and axle strength unless you're making LOTS of power.   That axle key is not a wimpy little woodruff model, it is a full length square cut key.  That design was used (with a bigger ring gear) right up to the fire breathing 413 Ramchargers drag car..   I saw lot of them run back in the day, even had one in a 58 Dodge Coronet, replacement for the 326.   Never saw one fail.

 

Brakes and/or ujoint issues are real though.   Thank goodness, my 56 pickup has 'normal' ujoints.  And I have a disk driveline brake that I might install just because I can.

[Los_Control]

37 minutes ago, kencombs said:

I really need to mention this, don't be afraid of rear end and axle strength unless you're making LOTS of power.   That axle key is not a wimpy little woodruff model, it is a full length square cut key. 

Says you .... I was able to force 3, 16D nails in mine as a replacement. Makes a nice and tight fit. 

 

I admit I'm terribly Biased on the tapered axle rear end. There are many old stories over the years where the key failed and left someone sitting at a stop light .... even if it did not happen to you.

A modern rear end is cheaper, offers several benefits .... mostly better performance with less effort and time.

 

Once I retired, I just do not seem to have time in my life for a tapered axle rear end. I just seem to value my time differently.

I'm going to pick on @keithb7 because he gets it and does it correctly. This is how you lovingly maintain a original car.

 

He is showing the front brakes on this video, rear brakes should get the same care every year ....

 

I'm just saying, Keith is a hardworking young man and goes to work everyday. And he has a hobby and can spend the time on the brakes.

I appreciate how he keeps a beautiful car in perfect condition.

If his wife car needs a engine rebuilt, it is going to the shop .... his house needs a new HVAC system, he is calling a professional ..... The man is busy and has no time to take care of all needs while still working a full time job.

 

I was the same way when working .... now that I'm retired .... My time is too valuable to spend it working on a tapered axle rear end.

I can replace it with a few hours worth of work and cut down on normal maintenance required for a original rear end, it will work better and have more safety with better brakes .... and nobody but me will know I did the upgrade.

I am just too busy and it is hard to justify my time to work on a 75 year old technology that is inadequate.

 

I had to do some kitchen plumbing last week that included a new kitchen sink.

After I got my rear patio pressure washed today and everything put away .... I need to go in and repair my refrigerator by replacing the defrost heater.

I need to do some wiring and make some mounts.

 

The wife car needs a new pcm installed ... My daily driver truck needs some basic work, after I get the 49 Dodge on the road .... The garden needs work, the little barn needs attention ...... My time is more valuable once I retired .... I got no time for a tapered axle rear end.

 

[kencombs]

7 hours ago, Los_Control said:

Says you .... I was able to force 3, 16D nails in mine as a replacement. Makes a nice and tight fit. 

 

I admit I'm terribly Biased on the tapered axle rear end. There are many old stories over the years where the key failed and left someone sitting at a stop light .... even if it did not happen to you.

A modern rear end is cheaper, offers several benefits .... mostly better performance with less effort and time.

 

 

Back when I worked on these things every day I heard the same stories.   Every single time it was after a brake job or something else that required removing and replacing the hub/drum.  Poor worksmanship on the job caused the future failure.  I want to run a 4.11 or so rear end with an A833OD.   Once the brake job is done, if it needs one, there are no benefits to swapping, other than the emergency brake and there are other ways to attack that. 

 

edit to add:  The number one cause of key failures, IME  is/was the use of grease on the taper.  The key really doesn't do much.   The taper, wedged fit, axle to hub is where the torque is contained.   Workshop manuals were explicit, those surfaces should be clean, dry and free of burrs.   Many 'mechanics' had difficulty removing them, so lubed up the taper to ease the removal 'next time'.   It worked, they came off real easy!  But next time was an unplanned removal.

Edited November 28 by kencombs

[keithb7]

Drag me in to this will ya? Lol. I am still enamoured by old cars. Their simplicity. Doing the needed repairs and maintenance on them. It’s not much work to me. Keeps me outta trouble.  Yes I still work full time. Another number of years before retirement for me. I don’t grasp the “time is more valuable after retirement”.  Maybe I will get it once I’m retired someday.

 

Yup, my old ‘38 is an old car. Old technology. Old axle. Old brakes. Ancient generator and regulator. Electric wipers were unknown still. But I like it. It takes me back to a simpler time where gas stations were all full-serve with energetic people who wanted to check your oil. Top up your rad. Clean your window. I’m not even allowed to do these things at a Costco gas station. They took away the paper towel. Get in, take your money and get out asap. 
 

Build your hot rods. Resto-mods. Or Keep it stock. Whatever you like. Whatever makes you happy. Have fun!

Edited November 29 by keithb7

[QEC]

On 11/24/2024 at 3:42 PM, BayArea48Deluxe said:

Any place to look that lets me know what parts are doable for my swap? 

There are several old threads with varying amounts of detail for this swap but IDK if there is/was a comprehensive list. Start reading and taking notes. I think Charlie is still making front disc kits;  olddaddy@rustyhope.com

[Loren]

Kencombs is right about the design. As far as keyed tapered axles are concerned, you do know they were used on midgets, Indy cars and are still used for land speed record cars. Yes you need a good Hub Puller and the knowledge of how to use one properly ( there is a technique for keys even with pullers ). For some of us one more tool is the charm of the thing! As some of us know there is a recurrent thread "Show us your tools".

 

What I don't get is why anyone would swap to the axles that are most commonly used. Those have the differential carrier built integrally. Meaning if you want to do any repair work or change ratios, you either pull the complete axle or you work on it under the car. No thanks! At least with the stock axle you can pull the third member and repair it on the bench or change it for one with the ratio you want.

 

As far as U-Joints and drive shafts go, if you don't like the stock one, change it. You don't have to change the whole axle to get Spicer U-Joints! Other MoPar cars of 40s & 50s had them AND they used the same axle. There's driveline shops everywhere that will be happy to make you anything you want.

 

The other objection is the brakes. Another tool for your toolbox. I have seen home made tools and cheapie tools available, so I don't think that argument holds much water. The real challenge is to understanding how to make the Lockheed brakes work properly and then do it. If you can't be bothered then why are you driving an Antique Car? Same with the parking brake.

 

The most popular axles for hot rods are the Ford 9 inch ( very strong but has considerable parasitic drag ), the Dana 44 ( integral differential carrier ) and the MoPar 8 3/4. The MoPar axle is strong has lots of ratios and limited slip differentials. It has a removable third member for easy service and ratio changes. It is the same design as the stock axle but has a 1/2 inch larger ring gear so it is stronger for the heavy horse power later V8s.

 

"But I want performance!" Guess what? An axle does not make horse power! Engines make horse power. Bigger stronger axles can take away horse power and they do not add it. Considering these factors there's nothing to be gained by changing the rear axle. If you can generate enough power with a flathead to break the stock axle...well I'd like to see that! 

[Sniper]

I used to know an old timer, since passed, that was active back in the day building hot cars.  He told me that the tapered axle setup would shear the key once power got up there enough.  The solution was to cut another keyway 180 degrees out from the original.  Howeer, and this is according to him, the ultimate solution was to replace those axles with later ones that were beefier, such as the 8 3/4.

 

Now granted, axles don't make HP, but they have to be able to handle it and it's a smart move to work back to front making a high power car.  Most build a stout engine then start replacing parts broken by that added power.

 

Based on the old timer's info I put a 9 1/4 in my 38 Plymouth.  I also added the benefit of modern, self adjusting, self energizing 11" drum brakes.  While you can make the older stuff work well, it's maintenance intensive in comparison.  I'd rather drive than wrench.