1966-76 9.375" Oldsmobile 12 bolt question

[funkhoss]

I have a question about the 1966-76 9.375" Oldsmobile 12 bolt axles: what is the diameter of the axle tubes? Is it 3", like the 10 bolts? Or is it 3 3/8", like the later 9.5" 14 bolt?

From what I understand, the differential itself is about as strong as a 9.5" 14 bolt. I'd love to put one of these in a 3/4 ton truck, so that I could run 2.56 gears. I could perhaps weld spindles on the ends and use full floating 8-lug hubs with custom (or re-splined junkyard) axle shafts.

I'm just wondering if one of these axles can carry as much weight as a 9.5" 14 bolt, which was rated up to 6,000 pounds GAWR from the factory.

Thanks for any information you can share!

[monzaz]

It CAn be done...BUT the tubes are smaller at 3" But early trucks were 3" tubes but I think all 9.5 truck rears were 3.25" tubes. Later they started to make the 8.5 / 8.6 tubes 3.25' so they can all use the same perches from 1/2" to 3/4" rears.
We have a complete 2.73 rear 9.3 car from 1971- 1976 Full size car.

Pinion is same as the 9.5 1.875 even takes the same pinion bearings.
Years ago we were going to take the 14 bolt TRUCK 9.5 and use them in cars...Sooo it is funny your going the other way...lol.

[funkhoss]

Thanks for confirming that the tubes are 3". One option for increasing strength would be to sleeve them on the outside with a 1/4" thick 3.5" diameter tube; another would be to weld on an axle truss (or do both!).

Another question: do you know which vehicles came with the 2.41 gears in this axle? I think I've figured out which ones had the 2.56, but not the 2.41.

[funkhoss]

So...I have a few more questions. : )

• Do 31 spline Ford 9" axles fit this axle? Or are the splines a different diameter and/or pitch? Being able to use cut to length Ford axles would be ideal.
• Is there a pinion yoke (or flange) available for the early, 28 spline pinion that will accept a 1350 u-joint? I'm guessing that any 30 spline flange/yoke from an 8.5" or 9.5" differential will fit the later 30 spline version.
• Does this differential have a threaded ring on one side for adjusting carrier bearing preload, like the 9.5" 14 bolt? Or does it have shims on both sides like a 10 bolt?

Thanks for your help!

[monzaz]

The early 9.3 Olds 1966 -1970 will have 30 degree pitch axles and sealed axle bearings. The splines are usually NOT compatible with the 31 spline Ford axle spline pitch.
The 1971 - 1976 era 9.3 Olds 12 bolt cover 12 bolt ring is a 45 degree axle spline pitch and should be compatible with the Ford 9" 31 spline.
The axle bearings are SET10 and Doubt they will be compatible with any ford 9" axle bearing.

As far as tube strength...Yes you might have to sleeve and or truss the tube if you are increasing weight load and or stress load.
Best to install FORD ends on the housing ends so you can get a better choice of disc brake selection if your going that route.

Yokes:
1966 -1970 early Olds 9.3 will have 28 spline yoke. NOT sure there is any aftermarket heavy duty yokes for that.
You can retro fit the older housing with the gears from a 1971 - 1976 era and use the 30 spline optional 8.8 8.6 9.5 9.6 yokes STOCK or aftermarket.

the 1971-1976 just seems like a better choice to upgrade for strength easier .

Carrier adjustment: Both 9.3 early and late olds FULL SIZE car carriers will have shims like a 12 bolt chevy on each side not spanners
Any rebuild kit will have a supply of those shims with a GOOD rebuild kit.
We have to make the 9.3 rebuild kit custom...Most all suppliers will not even get this kit correct as they do not know the rear your even servicing.

Jim
JD Race

[funkhoss]

Thanks so much for this information! It's really helpful!

One final question: how common is the 2.41 ratio in the later (1971-76) axles? Have you seen any 2.41 axles (or do you have any of these gear sets)?

[monzaz]

in the 9.3 I have not seen any 2,41 in 30 years....BUT I was not a BIG collector of full size car rears . 2.56 was most common then 2.73 ... a few 3.08 and 3.23 ratios and I believe I have NOT ever had a 3.42 either.
Remember full size cars were luxury...and they had BIG cube motors and really just did not need the gear to move the car with all the torque.
BUT they did need to make the car able to get on the freeway and cruise across country etc.
Not having OD this was it. gearing.

Jim
JD Race

[funkhoss]

Got it. Thank you!

I really appreciate this helpful information!

[monzaz]

That is what the forum and site is for.

I just wish we could find more parts for you....Things are thin out there.