Recently serviced anti-slip diff. for my 1968 98. Spent a lot of time locating parts and materials. Want to give info to forum members to save them the time.

FELPRO lists 3 differential gaskets for this car according to the local auto parts store computer. The only one that actually fits this car is FELPRO number RDS55009. The other 2 were an inch or so too small in diameter, even though they had 12 bolt cutouts.

Olds shop manual calls for no. 1050081 SAE90 differential lube. Local parts stores have lots of diff. lube, but none would guarantee compliance to the Olds 1050081. Went to the local Chevy dealer and they have GM lube 89021671 which traces directly back to the 1050081. They also have the required anti-spin lube additive 88900330, and direct replacement NOS steel filler plug 25522466.