70-Olds-442-convt

Are there any tell tale markings or other casting data on the W-27 rear axle that can verify it's real and original?

compedgemarine

I dont know on the 1971 version which just used an aluminum cover but the 1970 version the center section is aluminum with pressed in steel tubes.

My442

There is no 1971 version.

1970 was the only year.

If the center section and cover are aluminum, it's the real deal.

2blu442

I agree that if the whole pumpkin is aluminum its a real W27 rear end. At least I've never heard of anything else that looks like it. There should be casting numbers in the aluminum, you can post them here for others to verify. I know of at least two members here who have these in their cars. They can speak up if you need help identifying something on it.

Or are you asking if there's a way to know if it came factory in your car? If so, you'd need a build sheet that shows what options were put on the car on the assembly line. If you need more details on that let us know. John

Texas442

May want to read this also:

http://www.realoldspower.com/phpBB2/...887b6bfc4e0300

wmachine

This should be clarified. There was a W27 in 1970 *and* in 1971. In '70, it was the housing *and* cover, and in '71 it was the cover only. In '70, it was only available on the 442, W31, W32, and Rallye 350. The '71 cover was available on all A-bodies including the wagons.
Re the ROP post, I'm the one that gave Brian the note re the 351 produced through June,'70. With only 6 in the month of June, a reasonable guess for the year would be a total of 355 units. In '71, 159 W27s (meaning just the covers) made it on to production cars.

mmurphy77

I was told the W-27 cover in 1971 was a dealer-installed option only and never put there by the factory. Is this incorrect?

70-Olds-442-convt

Here are the pics I have of the axle.

Thanks for all the input.

wmachine

159 from the factory. Right from Oldsmobile computer printouts of production records.

svnt442

That is listed as a 3.91 rear.

Look here in the left column.

mmurphy77

Thanks Kurt!

Texas442

Just for fun only, can we take guesses as to what the distribution was among the 3 codes? Here is my guess:
SV 3:23 (20% of 355 or 71 units)
SX 3:42 (40% of 355 or 142 units)
SZ 3:91 (40% of 355 or 142 units)

stevengerard

Kurt, in 1970 was it available on all 442s Ior just W cars, W30, W31, W32s and the Rallye 350s?

wmachine

Thanks for bringing that up, as I miss-spoke in my earlier post.
In '70, the W27 was only available with the W30, W31, W32, and Rallye 350. Not the basic 442.

BlackGold

If that "M12" in the third picture is stamped into the housing, it is probably the assembly date and decodes as November 12 (probably 1969, unless they were still assembling spares for the parts counters in 1970).

The cast iron housings had a 1- to 3-digit date code cast in them. The aluminum housing might, too? If so, it should predate the assembly date.

leepear

My car is in Colorado at Level One Restoration so I can't get the codes off my w-27. As always an interesting discussion. Lee

1970 442 w-30
1971 442 w-30
1970 vista

leepear

Forgot to mention mine is a 3:91. I have owned a few other w-27s including a 3:23 and a NOS unit without gears and axle stamping. So you can mark me down for three of the lot.........Lee

BlackGold

Make sure we see pictures when it's done. They do beautiful work!

leepear

I had Gary post some shots of the w-27 on the web site. He will add a couple shots with all the stampings. Levelonerestoration.com

Lee

herpestes

add 1 more to the list 1970 w-30 with 3.91 gears

leepear

mine has a 0529 stamped on it. Does anyone know what that means. The car was built in February of 1970 and delivered in March. I would think the stamp would be the number produced or the stamp means something else.........Lee

442ric

The '70 W27 cover was a 12 hole cover. Was the accessory W27 diff cover (pt. no. 231026) a direct replacement 12-hole cover or was the over-the-counter part a 10-hole cover? Were there two different covers available over the counter for '70?

svnt442

Not for 1970. The only housing used in 1970 was the O-axle housing.

joesw31

I say the following:
SV 3:23 (5% of 355)
SX 3:42 (30% of 355)
SZ 3:91 (65% of 355)

I have two w31's with w27's, one has no date code on the housing, and other is "A15". Both of my units are 3.91 SZ code. I don't think they made very many runs of the w27 unit. If we could get the date codes together, we could figure out how many runs there were.

442ric

I'm still confused. I've seen the OEM 12-hole cover for the '70 W27 diff housing. I've also seen a 10-hole version of the W27 cover.

ROCKET VAPOR

IIRC, the 10-hole W27 cover version was never offered by Oldsmobile thru the dealerships. This 10-hole cover is just an aftermarket thing, like the W27 cover that is currently being made for Chevy 12 bolt rears.

442ric

That was one of my suspicions. It didn't make sense that Olds would cast a 10-hole cover for their 12-hole diffs.

wmachine

Come-on guys, please don't start any rumors here. You're not paying attention to earlier posts: In 1971 the W27 option was the cover only. And in 1971 the rears were 10 bolt corporate. So there are the *factory* 10 hole covers.

442ric

So, the '70, over-the-counter, accessory W27-style cover was also 10-holes? Or was the non-W27 diff also 12-hole?

mmurphy77

Would these 159 have it listed on the window sticker as an RPO?

ROCKET VAPOR

Thanks Kurt!

I guess I got caught sleeping in class

wmachine

Yes. Definitely.

Don't know what you mean by an "over-the-counter, accessory W27-style".
The parts books will show 2 different part numbers for the '70 and '71 W27 covers. The '70 will have 12 holes and fit the O-type, and the '71 will have 10 holes and will fit the corporate 10 bolt.

442ric

By over-the-counter I mean an item that was ordered from the dealer's parts department and received "over-the-counter," as an accessory, as opposed to receiving an item that was installed by the factory, in part or whole, as an RPO.

So, let me see if I have this straight. In 1970 you could order option #712/RPO W27 and you got a H.D., 10-bolt, 8 1/2" ring gear, rear axle assembly featuring an Al center section with a cast Al cover, designed with 12 attaching bolts. In addition, you could order the same diff cover separately, through the dealer's parts department, as accessory part #231026, to either replace a damaged W27 cover or to bolt onto a regular 12-bolt cover "O" diff, replacing its OE stamped steel unit. This "W27" cover would also fit late-'67, '68 and '69 "O" differentials.

For 1971 a customer could order #682/RPO W27, as a factory-installed option, which was comprised of just the cast Al differential cover, this year in a 10-hole version. The same cover could also be ordered over the parts counter as a dealer-sold accessory.

The only question I still have (on this subject) is, what is the accessory part number for the '71 cover?

joesw31

231090 1971 ALL - ALUMINUM - INCL GASKETS and BOLTS. Also if possible refer to the assembly manual for 1971, it shows the steel cover being removed, and the w27 cover being installed

442ric

Thanks all.

anthonyP

Did the W-27 cover, in '70 & '71, have special bolts? Were they black oxide or stainless steel?

Factory W-27 installation for '71 was low due to factory strike and no mention of it in the brochures.

Unless the dealer mentioned it, the buyer had no way of knowing about the W-27 cover. Was probably best back then for the buyer to review the Order Sheet themselves, so as to know what was offered for the model they were buying - as the dealer surely did not tell them.

s i 442

I drove/parted out this W-30 and it had a W-27 complete rear end in it, 3:42s. I put it in a 71 Cutlass S and drove it as a daily drive for 3 years then sold the car. Then the 71 S was flipped in a ditch and last time I saw the rear it was under a 68 GTO with a 454 Big block Chevy with two 4s sticking out the hood and thats been close to 10 years ago.

Let me clarify, The car had a complete W-27 rear but That doesn't mean it was the factory one.
I do know the car sat in a cow pasture starting in 1983 and I brought it home in the mid 90s. The rear had to be put in before 83.

wmachine

It really wasn't that obscure. It was listed in the SPECS booklet, which was every salesman's bible. There was no reason *not* to mention it any more than any other option. 1971 performance advertising was toned down from 1970 and unlike in '70, *none* of the individual performance goodies were featured in brochures.

junior supercar

black

anthonyP

My brother bought a brand new 442 in February 1971, and the salesman did not mention anything about the W-27 rear axle cover, nor any other performance options. My brother only had the '71 sales brochure to go by, which hardly mentioned any performance options, and what was listed in the high performance brochure in 1970. Fortunately, he did his homework before placing the order with the dealer.