Hi,
I was looking at my Cutlass the other day and remembered a picture I had taken about a year ago from Cutlass S Coupe I own. I haven't taken the rear cover off of the S, or checked the gear ratio yet, but was wondering if the different covers mean different things? I have searched and can't find anything definitive. My 1971 Cutlass Supreme Convertible 455, T400, has a 10 bolt 2:56 open rear end with the standard 10 bolt cover. The picture below is the the same as the cover from my 1971 Cutlass S 350 with an automatic parts car. The cover is also a 10 bolt but has the extruded curvature at the top like the picture below. Does the difference in the cover (the extruded curve along the top) have anything to do with the S being a limited slip or different style rear end?
Thanks
Will

 

The cover in the photo you posted is for a Chevy 12 bolt (count the bolt holes), which is not the same as the 12 bolt cover used on the 1966-70 Oldsmobile Type O axle. The original axle in a 1971-72 Cutlass would be a "corporate" ten bolt. The raised feature in the cover is not the same as the one in your photo.

 

If you read what I wrote, you will see I was using the picture as a “reference only” for the extruded curvature on the cover. The cover on the S car I’m talking about is a 10 bolt but has that curve on the plate like this one in the picture has. Just trying to find out if there’s a difference between the standard cover on my cutlass supreme and the cover on the cutlass S both of them being a 10 bolt but having different covers!

 

My guess is that the curved portion of the cover directs some of the lube that is being splashed onto the inside of the cover to the sides to lube the carrier bearings.

 

Post pictures of your cover.

The reason for the bend in the covers...Usually Chevy covers is that they had OILed bearings and the covers were designed to trough oil through a round casting hole outboard the carrier bearing which went into the axle tube and gave a better oil flow to the c-clip axle bearing which got oiled from the center section.
The early BOP rears were sealed bearing and did not need oil from the center section oil supply.
You do not even see that design anymore... Someone got paid for the design and then it just faded away ... just like always engineering at its finest...lol

Anyway that is the deal with the bend in the cover.

Jim
JD Race

 

Jim,
Thank you for the information. I have a picture of the round cover. I will get a picture of the cover with the curvature and post them.
Thanks
Will

 

The picture with the dirty cover is my 71 cutlass supreme. The one with the rusty cover is the 71 cutlass S.
Thanks.

 

Both are 8.5 rears -
The one with the trough is the Olds 10 bolt 8.5 and the scalloped cover below is the Buick.
SAME rear inside.

Why the different covers??? who knows... at this point GM is starting to change everything to run the same rear under every vehicle in the mid size from A-body to F-body etc.
Metric 7.5 is starting to be fazed into the smaller cars NOVA Monza Vega etc. and soon will be into the g-bodys and FULL SIZE CARS !!! UGH as HP is going down the drain soon.