VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Best option for rear end?

I have a 38 with a 4:22 beautiful car. I also have Master complete rear end 3:73 in my barn. I obviously want to put the 3:73 into the car. What is best way to do that? Complete rear end torque tube etc swap? Remove ring and pinion from one and put in the other? Swap the whole gear set ? By the way other than the complete rear end swap ill need some direction.... I have no torque tube experience. Thanks all! -John

I would use the 3.73. First replace the drive shaft bushings and inspect the side gears and bearings. Also replace the U joint.

Thanks Gene. To be clear you are suggesting taking the 3:73 master entire assembly and get it all ready to go and then swap everything. Drive shaft bushings I assume you mean the Oakey bushing replacement action?

BTW I am assuming my car has the 4:22 any way to tell other than counting teeth? Torque tube makes counting rotations challenging! :)

If it has a lot of power in high gear below 50 MPH it has a 4.22.
The number is stamped into the housing facing th front of the car on the right side as shown in the shop annual,

It wil be easier to work on the 3.73 while it is not in the car.

Hi John,

Do you know what year the 3.73 axle is? That could be a factor in your decision.

If I remember correctly the rear axle width increase 1 1/2” in 1938 compared the 1937. The motivation was to give more width to the rear seat passengers.

Spend some time with a tape measure to check and compare axle width as well as length of the torque tube. Also, look for any physical details such as brake line mounting, how the springs attach, etc. Not that it makes a difference but I think the axle vent breather location changed between 1937 and 1938.

The reality is that it is going to be about the same amount of work whichever way you go. You will probably want to replace the bearings and seals and bushings in the 3.73 axle anyway. So you will have it at least partially assembled.

I also agree with Gene that working on an axle out of the car is a whole lot easier.

Yes, just exchange the torque tube and not the complete banjo housing

Must be the 4:22 but ill check...

Sorry Gene when you say torque tube not banjo housing please be more specific. I thought i was removing and then installing the whole shooting match like I would an open rear end and housing :) thanks

If I understand Gene correctly he is recommending that you leave the axle housing that is in the car as is.

If you look at that housing you will see a series of bolts that hold the rear cover. You need to remove those so you can remove the block and c-clips to pull the axle shafts out.

On the front side of the axle housing you will see a series of bolts that connects the differential housing to the axle housing. If you remove those bolts you have an assembly that includes the torque tube, drive shaft, differential, and the differential housing as a single unit. The complete differential with ring and pinion, spider gears, and inboard bearings is within that assembly. That is what you want to replace.

The part that takes finesse is being able to slide the torque tube and axle shaft forward far enough to get the whole differential out of the axle housing. You might have to loosen the u-bolts on the springs and slide the axle housing to the rear. If you do that you will need to disconnect the parking brake cables and probably the brake hose.

The other key safety point is that the torque tube assemble is pretty heavy and awkward to handle. Plan on having help.

Practice by taking the 3.73 apart first. While you have the axle shafts out at least replace the seals.

Looked for 422 "stamping" and checked the book. I can only find raised numbers nothing stamped. numbers 204 (julian?) 59301 (raised) 4 on a raised block. All on the top right (passenger) side. I dont see stamping anywhere? Can someone give some more precise ideas? thank you.

thanks Rusty.. When you said "replace bearing and seals on the 373" where you assuming everything was getting replaced not just the TT etc. as you just described? thanks

This is one of those “while you are this far in” situations.

At a bare minimum you should consider replacing the bushing in the torque tube and the axle shaft seals. It is pretty easy to damage those seals when removing and installing the axle shafts. Replacing the driveshaft bushing is a whole lot easier when the assembly is out of the car.

Whether your replace the outboard axle bearings is more of a decision about how much they are worn and how quietly they were operating.

My recommendation for all seals and bearings was based on the potential that you would simply use the ring and pinion. If you are going that far into the differential then it just makes sense to do it.

The key point is your level of confidence that the 3.73 was operating properly when it was taken out of service. You also need to determine if it deteriorated while being stored. For example, did all the lube drain away for certain areas and allow parts to rust? That can be very damaging in this assembly.

Rusty, First thanks for the patience and details. I'm hanging on every word and by nature am precise so bear with me.... that said I agree and understand with your thoughts for sure. think I was reading into the previous comment too deeply. BTW do you know where that gear ratio stamping is on the rear? And yes I will practice on the 3:73 for sure.

You could put the rear on stands, block one wheel, remove your spark plugs, pop the distributor cap and turn the engine over by hand. You can measure the ratio and tell which one it is.

Don’t worry about the additional questions and request for details. It is the only way to minimize problems. We all are at different levels of experience and knowledge.

The 4.22 axle should have a letter “B” as a prefix for the number stamped on the right front side of the carrier housing. The 3.73 will have either a “C” or “CB” as a prefix. Plan to do a lot of digging and scraping to uncover the number.

Make sure you have a shop manual before you start this project.

As I noted before your biggest challenge is determining the condition of the 3.73 axle. The last thing you want is to go through all the work to make the swap and have problems with the replacement axle.

thanks.. this is out of 1937. Does that impact our thinking thus far?

Will be OK for the torque tube housing but not for the axle housing or axle shafts.

Therefore proceeding as you suggest.. everything right down the center replaced? thanks

I agree with Gene. You cannot use the full assembly.

The ”˜38 axle housing is wider and attaches to the leaf springs differently than a ”˜37.

I expect that there will be some other “gotcha’s” along the way. Based on what I read the ”˜38 axle shafts are 63/64” compared to the ”˜37’s which are 31/32”. All the bearings are the same for the 2 years so that should not present a problem. Just be looking for those detail differences. Most of them will not have any impact.

This swap has been done numerous times before. You are fortunate that you have access to a 3.73 gear set. They are getting difficult to find.

thanks all. I also have a 53 automatic car rear end just in case! :)

There will be little of that that will fit a 1938.

Fitting a Powerglide 3.55 differential into a ”˜37 to ”˜39 housing has been done a few times. A coupe of major differences are driveshaft length and the differences in splines. It takes skills and equipment that many of us do not have.

You will be successful with your current plan as long as the 3.73 differential is in good condition.

thanks Rusty... The Powerglide would be for plan B IF I even do it. Hoping I dont need it I know the 37 was working fine when removed. BTW I cannot for the life of me find that stamping. Have you see one? if so can you be a bit more precise as to its location? I just want to be double sure before I tear into things. Worse case ill count teeth. Thanks

the number is stamped into the front of the banjo housine between the bolts that bolt the center housing to the +banjo. The stamping is located in line with the right axle shaft or the 9;00 o'clock position. note they are facing forward,

Thanks Gene.. somebody treated the housing with POR 15 or another thick cover and so filled much.