Jono

Hi Everyone - I have a diff related question.

This is my first post, hopefully I don't ask too many silly questions because differentials aren't an area I have much knowledge in.

I'll give a quick introduction:

I'm Jono, and My father is Vince. I have been EFI tuning for 13 years, and my dad was a farmer.

My father imported a 1970 Oldsmobile 442 W30 from the USA a few years back (We are in Australia). The car was in good condition. Unfortunately the engine was very tired and needed a rebuild. We got a Olds 455ci engine built in the USA by some guy that said he specialised in the Olds 455ci but the builder burned us and sold us a defective engine. (Crank was linished too much, low oil pressure, and the idiot left a nut in the intake piping.. destroyed the cylinder head and piston in number 2).

We used most of the parts on the rebuilt motor - The new edelbrock alloy heads (number 2 was repaired), cam, block etc. Pistons and rods were replaced, and we used the crank from the original motor.

Anyway, the new motor runs great now. Heaps of torque. As us Aussies would say - It hauls ***!

But with this extra power, we need more traction. Unfortunately the diff is only one wheel drive.

We have absolutely no idea what we can replace it with. Dad said he would prefer not to use one of those locker style differentials that locks harder when more power is applied (I think they are called powertrax or something?) He wants something that is a normal LSD. I have heard that other models of GM vehicles may bolt straight in without much fuss at all. I was hoping someone would be able to point me in the right direction?

For example, there is a 79 Trans-Am LSD (2.41) available in Australia at a cheap price. I highly doubt it will fit, but it would be great to know what is a straight swap.

Maybe the question to ask - What is the easiest method to get LSD into this beast?

Thanks for your time and I look forward to your responses.

Jono

lemoldsnut

The trans am is a leaf spring rear end and the Olds is a 4 link style with coil springs. Much different. Pretty much any A body from 67-72 would fit. A few things will change here and there like u joint yoke or width on some but generally all of those will fit.

A body GM is

Cutlass
442
Skylark
Malibu
Chevelle
Tempest
Lemans
GTO


Hope that helps

Larry

Jono

Thank you very much for the reply Larry.

I have read some things about different numbers of splines or something across different models? Sorry about the silly questions... I really do have a very limited knowledge with this range of older vehicles.

Fun71

Also the rear from an El Camino, Monte Carlo, or Grand Prix of those same years will fit.

If you are wanting to swap just the differential from open to LSD then you need to identify what rearend is under your car now. The '70 would have come with either an O-Type 12 bolt, or if it was a Canadian built car it could have had a Chevy 12 bolt. Then over the past several decades someone could have installed an 8.2" 10 bolt or a corporate 8.5" 10 bolt. Take some pictures of the rear cover, the side of the center section, and the yoke and we should be able to identify what you have and give you recommendations on what you need.

joe_padavano

Let's back up.

Your 1970 uses a Type O rear axle. This was only used on the Olds Cutlass line from 1966-1970, and internal parts are completely unique to this axle. NOTHING interchanges internally. There are vendors who do sell posi carriers for the Type O. By the way, the fact that it has 12 bolts on the cover does not make it a "12 bolt" axle, as there are only 10 bolts holding the 8.5" ring gear to the carrier.

This car is an A-body, however, so any 1968-72 A-body axle will interchange. Some of these other axles have a different dimension from the pinion flange to the axle centerline, which requires a change to the driveshaft length.

Also, if the car really is a 1970 W-30, I sincerely hope you have retained the original heads and intake manifold, as these are worth considerable dollars (like USD $1500 for the intake and $4000 for the heads).

Jono

Hi Joe - Thanks very much for the advice. We still have the original heads, intake manifold, block etc so I will make sure that all of this is retained. I had no idea they were worth so much if they are genuine W30 items. I will look over the forum to see if there is some information on how to verify.

I've managed to get some pictures of the diff. I can see the first number (402227), but not the second. Unfortunately it was on a hoist with another car underneath in so I couldn't walk under. (It is in the process of getting the T400 auto overhauled. The one that came with the car wasn't in very good condition.

Here are some pics: (Sorry about the size)

j4Dw6Xo.jpg

TTysLmS.jpg

BS69cSN.jpg

JTp59eY.jpg

VMhzyzj.jpg

EspHHqR.jpg

Jono

Thought I had better post some pics of the actual car too

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InHsxl7.jpg

d3srAkq.jpg

lemoldsnut

Joe is so right on this. If it is and it sure seems to be a true W30 then fix what ever is wrong with the 12 bolt type O rearend. Supercarsunlimited.com can be a big help with parts for it. Get ahold of them they can provide most parts for these. Plus lots of knowledge.

IF the SE code on the axle tube is correct and I decoded it correctly you have a non-posi 3:23 rearend.

Jono

haha I agree - I think it will be too good to be true. And we aren't that lucky!

As soon as I get some time I will be grabbing my dad and going over everything. He messaged me before and said it isn't the original engine. Not sure on the rest of the car.

BangScreech4-4-2

That sure as heck looks like a Chevy 12-bolt to me.


Car looks great!

joe_padavano

Look again. What you think is the inverted "V" notch on a Chevy cover is actually a reflection in the very shiny black paint on the Type O cover. The notch in a Chevy cover is much closer to the top, as shown in the second photo below.

JTp59eY.jpg

Octania

C type covers also have a prominent rib between each pair of cover bolts. Easy to spot even from afar.

BangScreech4-4-2

Sure as heck looks like an O-type to me ...

pmathews

JD Race (monzaz) helped me with axles for my O-type, make sure you reach out to him, he's super knowledgeable. He's a frequent contributor on this board

http://stores.ebay.com/JD-RACE-AND-RESTORATION

BlackGold

Just to confirm for those still wondering:

402227 is indeed the casting number for the housing of the type "O" rear end used in 1970. 12-bolt cover, 10-bolt ring gear.

As others have said, parts are hard (but not impossible) to find. Unfortunately, the posi carrier you desire is one of the hard ones, and you have to make sure to buy the right one to go along with whatever ring and pinion set you want to use.

Last I checked, Supercars Unlimited sells a new posi carrier you can use. It's not a factory unit. It's something originally designed for a different rear end then modified by Supercars to fit yours. Make sure you understand which gears, bearings, axles, etc. must be used with this unit before you buy.

There may be other options out there. Otherwise, an expert like monzaz can walk you through this.

pogo69

what gears do you have in the type o now? with limited slip your still going to smoke up the tires traction wise...i never felt that much more traction in reality with the limited slip....car still goes sideways

pogo69

and another drawback is you cant use aftermarket gear sets in these carriers they have to be original GM gears unless they came out with some new tooling

Fun71

That's not quite accurate. I have a set of Richmond Gear 3.90s in the garage. These are older gears but for many, many years Richmond (and another company I can't remember) made 3.42, 3.90,and 4.10 gears for the O-Type and I would guess there are still some out there.

sammy

What colour is your? Does it match the paint code on your cowel tag?. I am about to paint, and I am in search of colours

oldsmobiledave

To be complete you must also state that these gears are only to be used on the 3.08 & 3.23 carrier. They will NOT work on the 2.56/2.78 carrier or on the 3.42/3.91 carrier.

Fun71

That is correct. More information: several years ago Brian Trick said he had made some ring gear spacers so that these gears cold be installed on the 2.56/2.78 carrier. I have no idea if he still has any of those spacers, though.

monzaz

We have all the 12 bolt olds parts still available
We have Eaton Posi units
rebuild kits
axle bearing and seal kits
We can make you custom Moser axles in 28 or spline to fuit the stock housing.
we can make you a FULL spool carrier
we have Power trax units to fit into your open non posi carrier (28 spline only)
and
3.42 and 3.90 gear sets that fit the 3.08 and 3.23 Original GM carrier
we can even build 2 series posi units for you guys that like to have posi and still freeway roam. Jim

J D

Jono

Hi JD

I will be in touch with you when I get some time.

Just a quick question - Is the "Eaton Posi unit" what you call a limited slip Diff?

monzaz

Eaton posi is a Manufacture of Chevy line of Limited slip differentials back in the day. They were first used in the 1964 Pontiac Olds 9.3 and 10 bolt 8.2 1964 drop outs third members. After that in 1965 Chevy line nade a deal for the 12 bolt and 10 bolt chevy rears to be produced by EATON MANUFACTURING to provide the Limited slip differentia units. Buick Olds And Pontiac FuLL size cars also had contracts for the Eaton units - The A-body GM Buick Olds and Pontiac used the Auburn Manufacturing for the Limited slip units 1964-1972
Borg warner (like and auburn unit was also used in the latter years of the A-body muscle car era 70-72 for the chevy c-clip and the 10 bolt 8.5 rears.

So when you say POSI that is really a Chevy and Buick Limited slip nick name.

LIMITED SLIP DIFFERENTIAL (LSD) si the proper industry term for both wheels providing power to the rear wheels equally in straight away and having the ability to bias the axle grip from left and right tires in a turn (to release the in turns) Hope this helps explain everything. Jim

Other nick names for Limited slip by other companies-
AMC twin Grip (spicer unit Clutch)
FORD Trac Lok (clutch)
Dodge Sure Grip (cone Auburn) and Power Lock (clutch)
Plymouth Sure grip (cone Auburn) and Power lock (clutch)
Oldsmobile (anti spin)
Pontiac (Safety Track)
Everyone had a nick name and or manufactures nick name for LIMITED SLIP DIFF.

So YES eaton is a limited slip diff (in the world of rear differentials.) Remember Eaton is a HUGE manufacture of the world goods.... It is but a small little area of the company.