Well....I was wondering the same thing. When I did my rear axle service I was told that GM no longer uses rear axle gaskets! I went to a couple of more parts stores with no additional information. But to my suprise, when I performed the service there was a factory gasket in place! Go figure.
I replaced the rear axle gasket 01/26/02 on my 2002 D/A with the 14 bolt, 11.5" AAM rear end. At that time, the GM # was 12471447.
I think I had to take bad the first gasket they gave me, which was the wrong one. Part #'s at GM seem to change from time to time.
I just use some good 'ol RTV sealant, like UltraCopper. Make sure to get any left-over residue off both the cover and diff, put a small bead on the cover and button the thing up. The best results are achieved if you let the RTV 'set-up' for +/- 24 hrs before adding the lube. This has worked for me for many years. Cheers.
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