Oldsmobile W27 rear end differential housing

**Stefano** · #1 10-24-2011, 05:58 PM

Oldsmobile W27 rear end differential housing. This is the aluminum center section which was available as an option on 1970 W Machines.

Code SZ is 3.91 posi

**markjohnson** · #2 10-24-2011, 07:10 PM

That's one of the neatest options that Oldsmobile ever did. I'm pretty sure that the entire aluminum center section was one-year-only (1970) but when it came back in 1971-72, it consisted only of an aluminum rear cover on a standard iron axle.

**SmallHurst** · #3 10-24-2011, 07:10 PM

[img]<<GRAEMLIN_URL>>/drool.gif[/img] That is a sick chuck of change there! Love to have one, but worth enough to buy another car with.

Plowman · #4 10-24-2011, 07:44 PM

Look's so cool, I know it's rare,is that rear,the aluminum center section,any stronger.

**SmallHurst** · #5 10-24-2011, 08:10 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Plowman</div><div class="ubbcode-body">Look's so cool, I know it's rare,is that rear,the aluminum center section,any stronger. </div></div>Actually, it's weaker. It was an idea to reduce unsprung weight. Stress cracks would show up eventually.

**Stefano** · #6 10-24-2011, 08:24 PM

The warranty replacement was the iron Olds 12 bolt, if that says anything. Only approx 355 were ever factory installed on W machines.

LeeP · #7 10-24-2011, 08:48 PM

My 1970 olds was ordered with the w-27. During the restoration the expert on this rear end Joe from Texas, restorer and I agreed the differential came with aluminum anodized bolts on the cover. So mine looks like the one in the picture with different bolts. In addition since mine was a California purchased W-30 one of the top fins on the cover was trimmed to allow for the extra fuel line for the California smog. I thought my cover was junk till I found the dealer bulletin on the cover. Huge research required for only one aspect of the restoration, but fun.

Lee

**Stefano** · #8 10-24-2011, 10:47 PM

The bolts on the one I posted pics of are to be original. However, I would not think that the restorer paid that close of attention to the coating. I have a pre resto-photo I'll try to scan.

Cool info!

LeeP · #9 10-24-2011, 10:56 PM

I have seen them both ways but Joe worked for Oldsmobile in the day and has two w-27 w-31s and is the most knowledgeable person on the w-27 in the world. Mine was original too when it was restored. During a restoration you have to go with the best information you can get. If I were judging your car I would not take off points for the bolts. My car will be at a few events in November SEMA and Muscle Car Nationals. When it is out I will try to get some nice pictures of the detail of my restoration.

Lee

**Stefano** · #10 10-25-2011, 01:03 AM

Here is the pre restoration pic.

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DW31S (12-17-2023)

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DW31S (12-17-2023)