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View Full Version : "Flat Bottom" S3 Rear Axle Case?


jac04
03-05-2009, 10:11 AM
I'm ordering a new rear axle case from PA Blanchard for my Lightweight, which is a Series 3 and appears to be 1980 or 1981. The part number for the case is FRC3367.

PAB is asking whether or not I want a "Flat Bottom" axle casing. They stated that the later style casing is flat on the top and on the bottom of the axle case. Mine appears to be rounded top & bottom. They told me that they are interchangeable.

Has anyone ever heard of this "Flat Bottom" case? Anywhere to find a picture of one?

Thanks,
Jeff
gudjeon
03-05-2009, 10:24 AM
The series 3 diff case is indeed a "flat bottom" casting. It differs from its predecessor in this way and having the seal housing as part of the same housing. Ser 2 housings had a separate ally seal housing that bolted on. From my experience, they both share the same seal.

When I swapped out an old ser1 housing, I had to remove a couple of alignment dowels. These must have been made redundant on the ser 3 diff at some point, but it does not affect anything once assembled. :thumb-up:
JSBriggs
03-05-2009, 10:26 AM
Yes, the NAS coilers have a flat bottom housing. I havent seen any late S3 housings, but i would imagine they have them. If its an offroader, I would prefer the flat bottom.

Give me a few minutes, I have both out in the shop, ill get a side by side pic.

-Jeff
Edit: Both of these housing have been modified, but you get the idea. The top one is the traditional series housing, the bottom one is a later (87) coilsprung housing that has the'flat bottom' notice that the drain plug is offset, so scraping over rocks is less likely to foul the drain plug.
jac04
03-05-2009, 11:09 AM
The series 3 diff case is indeed a "flat bottom" casting.
Yes, But I'm talking about the fabricated Axle Case itself, not the cast Diff Case.
jac04
03-05-2009, 11:38 AM
OK, I just found out the answer to this question. The "round bottom" axle case will have the drain plug at the bottom in the middle. The "flat bottom" axle case will have the drain plug offset slightly to the RH side and recessed. Mine is offset & recessed.
gudjeon
03-05-2009, 09:01 PM
:o oops!