Do all '71 and newer 10-Bolt rear axles have smooth rear axle covers and bolt-on axles? Have a '71 Olds 10-Bolt rear axle that has a partial Chevy-like brow in the cover, and clip-on rear axles, supposedly thought from '71 442. Do only Chevy's have the brow, either partial or full, in the axle cover and clip-on axles, and Canadian built Oldsmobiles? Still trying to find the axle code stamp.

Thanks for your assistance in determining if an Olds rear axle.

 

Hi Anthony, welcome to the site! Every 71-72 rear end I've seen had the smooth cover and bolt in axles, but I'm not an expert on this topic. Someone else will have to chime in who knows more about it than me. I do know the A-body rear ends will interchange as I've got a 1972 Che*elle rear end under my 1970 442. I had to get a funky u-joint though to match the Chebby yoke to the Oldsmobile driveline. If I remember right the Olds is longer from one cap across to the opposite cap. But the local NAPA parts store had a u-joint on the shelf that did that. Have you looked through the Wiki site and surfed the Drivetrain Differentials section yet? You can use the search function to see what has been posted in the past. John

 

Does the brow on the cover go from about 12 oclock to about 2:30-3:00? If so it a corp 8.5. Not all of them had that cover, don't know if it was an assembly plant location or what. JKaz

 

The Olds axle will have a smooth cover and bolt-in axles (no C-clips). Is this a Canadian-built car? Those may have gotten Chevy axles.

 

71 Olds 10 bolt covers had the chevy wrinkle. It"s hard to tell them apart but I would bet you have an Olds rear. This is a 71 Olds 10 bolt. It has bolt in axles. I rebuilt the whole rear. The Olds 12 bolts have a smooth cover.

 

Anthony, welcome to our site.

 

Thank you. Welcome to be aboard.

 

Thanks to all for their input.

The cover does have the 12 to 3 wrinkle, not the full wrinkle from 9 to 3, as the Chevy axles seem to have. It seems the only question left is the clipped-on rear axles. I will try to keep looking for the axle code, for as far as I know, each GM division had its own codes.

The axle is hopefully from my brother's '71 442, a 3.42 posi unit. It was taken out years ago and stored while the car was raced, and now were trying to determine if it is the correct axle.

The car was built at the Framingham, MA assembly plant in February of 1972, after waiting months for the GM strike that year to end.

Thanks again,
Anthony

 

Hi.

Does the rear axle on your W-30 have cones, or clutch type, positraction?
The rear axle we have is supposedly a '71, but it has a clutch type positraction
unit, and "C" clips. It was thought all '71 and later rear axles had the cone type
positraction. The '71 442 was built in Framingham, MA.

Thanks,
Anthony

 

Hi.

Also, where is the code stamped on the passenger side axle
on your rear axle assembly? I had thought it was located in
the past, but it cannot be located now with the pitting on the
axle tube.

Thanks,
Anthony

P.S. - My friend thinks it is a Chevy rear due to the cover, which is identical to
the one on your W-30, and the "C" clips.

 

Hi.

How do you tell the difference between the '71 10-bolt carriers, being those
that carry 3.42 and higher (numerically) gears, and those with 3.23 and lower
gears? Also, how would you differentiate the same with 12-bolt carriers?

Thanks,
Anthony

 

on your 10 bolt housing the code is on the front side of the passenger tube. the Otype 12 bolt housing it is on the back side of the passenger tube.

 

10 bolt pictured on the frame is a 8.5 10 bolt Olds rear with bolt in axles and 28 spline posi (clutch type trac lock.)
The ratio series gear break on the 8.5 units are as follows
2.41-2.56 = 2 series, casting numbers for bolt in axle is 726 and the c-clip casting number is 410409
2.73-5.57 = 3 series, casting numbers for the bolt axle is 725 and the c-clip casting number is 410408

12 bolt olds 'O' type posi LOOK THE SAME and even use the same clutches but are totally different...
12 bolt olds A-body rears come in to axle shaft spline counts 67-68 are 31 spline in the HP W cars and the 28 spline was for most of the other 442 etc. cars from 67-70.
Carrier break 2 series are 2.56-278 posi casting number 673 28 spline axle
carrier break 3 series are 3.08 3.23 posi casting number 671 28 spline axle
carrier break 4 series are 3.42-4.33 and UP posi casting number 588 28 spline axle
carrier break 4 series are 3.42-4.33 and UP posi casting number 672 31 spline axle

EaCH SERIES WILL MOVE THE RING GEAR carrier mounting flange about .200 to the center, each series up.

THe 8.5 and the 12 bolt olds GUTS are NOT interchangeable PERIOD. Only the positraction /anti slip clutches are interchangeable that is it.

Even the axles have different degree cut splines for the 28 spline axles.

 

nythonyp: Are you sure there are clips? It adds up other than that.

Jim, as I'm reading this the posters rear is a correct 10-bolt 8.5 *except* for clips. Could that cover fit on a Chevy rear? Ot could a Chevy carrier with Chevy axles and clips go in the Olds housing?

 

Thank you to everyone for helping with this perplexing mystery. With
the information received, I will try to solve the mystery of the 10-bolt
rear axle, and identify its origins.

Anthony