I think I need to do a rear axle gear oil change. 1988 5th ave 32,000 original miles with the original rear axle oil. The rear axle oil is full with no drips, just a little sweating. Do you think I should use a gasket, or Permatex gear oil gasket maker ? I can see the original orange RTV sealant around the cover. Is there a specific gear oil that would be best. it is an occasional driver car right now. Thanks for the advice.