I think Jack was thinking the other post asking about sheet metal parts. Dextron hydramatic fluid is correct for our cars. [ dextron keeps upgrading, I think it's now Dextron IV or V] the gaskets that might leak could be the one between the flywheel and transmission, or the rear seal one [where the driveshaft moves in and out]. The rear end should be a high grade gear oil - ask your local auto parts people. If you have an owners manual it will tell you the weight to use [80/90, 90/140, etc]. If you don't have the manual check the 'Circle KF' site for the owners or shop manual specification pages. The seals to watch would be the pinion seal, and inner rear axle seals but probably not the gasket at the differential. If needed, we do have some gaskets, seals, and a Hydramatic rebuild kit.