I have a 1948 oldsmobile 4 door.

On my way home last week, I heard the horrible sound of my differential chewing itself up. I limped it home, but it's on the verge of seizing. There is not a mechanic in range of me who is willing to try to rebuild it. My regular mechanic said if I can't find a replacement, that he'd help me out with replacing the rear end with something more modern, if I can find something that matches the dimensions.

So I have two questions.
1. is there anywhere that sells reliable rebuilt differentials for my 48?
2. What common modern rear end do people use to replace the original rear ends?

 

As far as I know . All 37 thru 48 Oldsmobile and Pontiac diff center sections will interchange as a unit .
1949 thru 52 Olds and 1949 thru 56 Pontiac will also interchange , but a two sized stud (made by Dorman) will have to be used to bolt the diff to the housing as the bolts were larger . Also , the 49 and up ring gear is slightly larger so the housing may have to be ground out slightly larger for the ring gear to fit .
I once put a 54 Pontiac rear section in a 37 Pontiac this way .

 

You need to send a PM to one of our members, monzaz. He professionally builds differentials and will surely know how you might go about repairing or replacing your differential.

 

Best thing we need is total width drum to drum

Wheel Bolt pattern 5 x 5 or 5 on 4 3/4" etc.

I assume this is leaf spring ? y/n
What is the spring perch center to center.

Jim
J D Race

 

Coil springs , radius rods , panhard bar , and lever shocks , Jim.
5X5 wheel bolt pattern .

 

Well I guess will need some pictures...lol. Jim

 

Have you popped it open? The axles on those cars are really weak.

 

I can get the drum to drum measurements when I get home tuesday. I will get the bolt pattern tuesday as well.
They are leaf springs, my mechanic says he can move the leaf springs as needed.
I have not. I assume that means you are advising a complete replacement for the rear end?

 

Yes that is best if your car will be a driver... 10 bolt 8.5 camaro or nova are usually good fits and you can replace your leaf spring perches as necessary... That is what Tons of people do. lEAF SPRING REARS ARE THE EASIEST TO CHANGE OUT AND REPLACE AS YOU CAN INSTALL THE PERCHES ANYWHERE AS needed... sorry bout the caps... not yelling.

 

What years work for the camero & Nova? Are they the same bolt pattern or will I need new rims?

 

You did not get us your info yet? How can we compare?
All Camaro Nova A-body ec are 5 on 4 3/4" wheel bolt pattern
MOST full size cars are 5 on 5 wheel bolt pattern .
You did not measure the width yet so there is really no need to go further till you measure your diff. drum to drum over all width

 

Gotcha! I misunderstood.

Outside of drum to outside of drum is 62".
backing plate to backing plate is 56 1/2".
My bolt pattern is 5 on 4 3/4.

I've also taken some pictures.

 

Ok... I hope your going to simplify all that. The 2 traction BAR (these were also used in 2wd chevy PU trucks too) / suspension NASCAR bar arms not an issue. spring perch can be moved also. The can behind the brake drum backing plate? Do not know what that is all about...some kind of suspension load sensing item? (is this really needed?)

Looks like fun ONE...???

 

That's a lever type shock absorber Jim .

 

I would dump that for newer technology and get the basic shock.

 

That sounds like a good plan. Do you need more measurements to be able to know what years of nova / camero rear ends would match my car?

 

You need to measure your total drum to drum OVER ALL WIDTH of the rear. Also you will need the wheel lug bolt pattern circle (5 x 5 ) 5 x 4.75? Something like that.
The rest you should be able to transfer brackets etc

You can run shocks anywhere you want and tailor them at angles that will help the suspension react to the way your going to drive it.
Summit / Jegs / etc sell brackets to weld to the tubes.
Everything else should just go back the same way as stock . Stay with GM rear as this will keep the pinion offset fairly centered as it looks like your rear is.
Ford and Mopar are heavy to the passenger side and will cause major headache and re-figuring the housing chopping cutting ... stuff i am sure you want to avoid.

Need a width and a wheel bolt pattern then we can help further.

 

Outside of drum to outside of drum is 62"
The bolt pattern seems to be 5 X 4.5.

 

Do you know how to measure the wheel bolt pattern? Even wheel bolt pattern is center to center to stud across from each other.
Odd wheel bolt pattern is outside of stud thread edge to center of a stud across the center left or right of dead center stud.

 

If that width is correct... a Camaro second gen 8.5 10 bolt (61") drum to drum would be a good base to stuff under there and you will only be 1/2" narrower on each side then it will give you some room for slightly wider tires for the rear if you like. IF you need it exact 7/16" or 1/2" wheel spacer can be used too with out any issues.

This rear has very little to remove from the tubes so you can put all your brackets from the original rear in place. Camaro is 3" tube like your original also.

 

Then I did that wrong. I'll get the correct measurements in a few hours when I get home.

 

So this should be 5 on 5 correct?

 

5 X 5 MAKE MORE SENSE FOR A OLD CAR.

We can make axles 5 on 5 for the camaro rear. no problem

Another rear that might be better a 1978 -1997 Full size sedan 10 bolt 8.5 with 5 x 5 bolt pattern Buick Olds Pontiac sedans full size cars. You will have to cut more off the tubes...But you will have the 5 on 5 bolt pattern ANDE the exact width as your old car. Jim

 

Awesome! Thank you so much for the help.

 

My mechanic is concerned about the 87-97 rear end, as he believes those would have been front wheel drive. Was 97 a typo, or is my mechanic unduely worried?

 

Actually 1996 would be correct You have to use Rear wheel drive cars obviously Impala SS, Caprice, Road master....NOT WAGONS.

 

Is it that tough just to find a replacement original? It sounds like from Charlie above, that these rear ends were used in Pontiacs as well, so that gives you a much bigger pond to fish in. Maybe hit up the Pontiac folks.

 

??? Do not ask me I do not mess with anything older than 55 What Junk yard is going to have a 40's car?
We do not have any cars here older that 2000. Ohio.

 

Finding another rear end I don't think would be too tough as long as you're willing to pay for shipping. There are several wrecking yards across the country that specialize in vintage cars and of course there are individuals that have stock piles of old parts too. The real question is- can one be rebuilt? Are there seals, gaskets and bearings available? Is there someone willing to tackle the project? I don't know the answers to these questions. I'm certain it can be done and there are people that can do the work, but my limited Google search indicates that they are likely off the web and phone calls and emails would have to be made. I thought perhaps someone here would know of such a service, but maybe not.

 

trouble with old mechanical parts...When they are not being used...THEY RUST UP and seize Engines transmissions rear ends. ANY parts not cover in oil are doomed.