Hey everyone,,, I was told this was the original differential form my 442,, I found codes but cant decipher them,, it has 3.90 gears,, 10 on the pinion and 39 on the ring

 

The 442 i have has 3.08 gears
The axle is stamped SD

 

SB axle code translates to a 2.73 axle ratio with anti-slip.

 

So then the ratio has been changed,, what about the cover? I have never seen one like it... is it a 8.2 or 8.5?

 

It's an 8.5" corporate 10 bolt.
Block O on the front where the axle tubes insert into the center section.
Drilled boss on top for the brake hose.
Two parallel ribs.

 

The cover is correct. Oldsmobile 8.5" 10-bolt rear axles had the trough in the round cover from the 12 to 3 o'clock position to funnel the rear axle lubricant to the side bearings. The Buick version did not have the lubrication ports in the housing and had a cover with scallops at the 3 and 9 o'clock positions.

 

Yes this is an 8.5 as all have agreed.
Doubt that is original untouched rear. The passenger bearing cap is on wrong. ....Wonder what else is wrong.

Arrows point to the outside toward the wheels on them bearing caps.
Looks to be the original carrier (bolt in axle 725 casting.

Cover is correct for the OLDS 1971 -1976 rears with bolt in axles.
Olds used BOTH the Olds and the Buick with the scalloped cover.

Show the other bearing cap will see if that is on correct.

Jim
JD

 

The left side cap is correct, it came without axles or backing plates

 

Sure looks like a 3.90 gear...Thick enough for sure.
Yep the right cap has to be flipped. arrow pointing out on the upper part of the cap. Hope they did not mix them up left to right either.
If you look inside the carrier before cleaning it you might see PAINT swipe that line up the caps reference to the case.
Take care, Jim
JD Race

 

The stamping indicates it is an Olds axle (O), and the ordinal date shows it's very early production (004). Jim has you covered on everything else. He's a wizard of rear ends. BTW, if your gears have been changed from OEM, have you converted your trans drive/driven gears so they reflect accurately on speedometer and odometer?

 

Thanks for all the Info guys,, I will pull the caps off and see if there is any kind of a paint mark... As for the speedometer gears I have replaced the driven gears a few times to get the speedometer close.. The car does have a 4 speed... From what I was told the rear differential was swapped out when the owner was going on a road trip from the east coast to New Mexico and just never put the original back in.

 

I have a set of axle shafts if you are interested. I was just about to post them in the Classifieds "free to a good home" to see if anyone needed them before I sent to scrap. If you want them message me and we can work something out.

For anyone else who might have one of these 71-72s with the 8.5" Chevy rear end and bolt in axles, I had Moser template them earlier this year so you should now be able to order 28 and 30 spline replacements (although they might not show up in the catalog)

 

They already have the specs - We have been making them for many years now.
You can see your axles have the GOOD old straight bearings on them.

If someone can reproduce them we would all be in great shape...
Jim
JD

 

I figured I couldn't be the first person to ask (Moser) but when I talked to them on the phone they said they didn't have specs and needed a sample sent. Oh well...keeping FedEx in business I guess...

 

Moser.... Just like everywhere in the world these days... NO Thinkers. They just do that days work and hang it up. IF they were smart they would file stuff.
I give our old invoices to get the same shaft built over and over.