48 olds differential is dead

Old June 6th, 2019, 06:04 PM
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48 olds differential is dead

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?
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Old June 7th, 2019, 06:58 AM
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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 .
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Old June 7th, 2019, 07:17 AM
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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.
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Old June 8th, 2019, 11:42 AM
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Retro fit rears

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
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Old June 8th, 2019, 06:22 PM
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Originally Posted by monzaz View Post

I assume this is leaf spring ? y/n
Coil springs , radius rods , panhard bar , and lever shocks , Jim.
5X5 wheel bolt pattern .
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Old June 8th, 2019, 08:59 PM
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Well I guess will need some pictures...lol. Jim
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Old June 8th, 2019, 09:50 PM
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Have you popped it open? The axles on those cars are really weak.
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Old June 9th, 2019, 03:47 PM
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Originally Posted by monzaz View Post
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
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.
Originally Posted by monzaz View Post
Well I guess will need some pictures...lol. Jim
Originally Posted by oldcutlass View Post
Have you popped it open? The axles on those cars are really weak.
I have not. I assume that means you are advising a complete replacement for the rear end?
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Old June 10th, 2019, 09:07 AM
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Originally Posted by kylevp View Post
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.
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Old June 11th, 2019, 02:36 PM
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Originally Posted by monzaz View Post
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?
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Old June 12th, 2019, 05:43 AM
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???

Originally Posted by kylevp View Post
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
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Old June 17th, 2019, 04:13 PM
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Originally Posted by monzaz View Post
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.






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Old June 17th, 2019, 11:38 PM
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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...???
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Old June 18th, 2019, 06:35 AM
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Originally Posted by monzaz View Post
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?)
That's a lever type shock absorber Jim .
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Old June 18th, 2019, 08:28 AM
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shocks

I would dump that for newer technology and get the basic shock.
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Old Yesterday, 10:42 AM
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Originally Posted by monzaz View Post
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?
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Old Yesterday, 08:57 PM
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measurements

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.
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Old Yesterday, 09:59 PM
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Originally Posted by monzaz View Post
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.
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