Differential gasket

You'll likely get RTV suggestions here as well...

I prefer to stick with gaskets....Sometimes I think the world is stuck together with RTV *G*

Any online parts supplier will have them...I surprised that Autozone, Kragens, or NAPA doesn't....try Summit...

I'm assuming your switching complete center sections and that the new one has the appropriate yoke on it for your app. Otherwise, you'll need a new crush sleeve to re-set the pinion pre-load...at that point, a new seal would hurt either...then there's bearings...hehehe

If you want to share the particulars of the swap, maybe we can help further...

Good luck!

Pat,

I really would like your help on this task I'm doing.
This is my first time to remove the center section.
At the same time, the FMX will be replaced with a C4.
C4 came from a '68 coupe and was working when removed.
Should I do a complete rebuild or just install it in my car?
I also have the driveshaft from the '68 coupe.

I will send you a list of part numbers I have on hand.
Hopefully parts I have are all OK.

You're doing a number of things here, all of which need to be done correctly for a good long-term outcome.

My first suggestion, if you don't already have one, is to purchase a good service manual. I would imagine VMF'ers have discussed this subject before as to which is best. A Haynes manual came with my D-coder and it has pretty good info but I have heard good things about the Chilton manuals, among others.

Regarding the trans...if it came out of a running car and worked well, I would just perform routine maintenance on the unit (drain converter and trans and change filter and re-fill), along with an inspection of the inside of the pan for debris. You could install a shift kit at this time, which would make inspection of the hard parts easy (valve body comes out)...unless there was something obvious going bad, I'd just leave it alone. The trans in the D-coder looked like new inside at 178K when I put a shift kit in it (OEM unit, never rebuilt) and is doing just fine as it prepares to turn the odometer over once again.

I'm not real familiar with FMX vs C4, as far as X-members, driveshafts, etc. but will bet it'll be an easy swap. The service manual will detail the step by step...just remember, if something doesn't seem right or you get stuck, stop, step back and think about it (post a question here if necessary)...don't rush...