I'm a dummy... The fill & drain plugs in the diff were frozen as well, so I had to remove it from the car to work on them. Did figure out a little trick to getting them loose.

I pulled the mustache bar off and installed it on the diff to act as a reatction bar so it didn't roll around while I stood on the pipe wrench to break the plugs free. Worked like a champ. Filled it with MT-90 and re-installed with no problems.

Also installed my new aluminum radiator and the engine underpan. The radiator sits a bit lower than the stock unit, so I had to install some 1/8" spacers and gently bend the pan edges where the interfred with the lower front corners of the radiator. Everything fits fine now.

Hi Julio:

Good tip... and always a good reason to keep a spare mustache bar around.

I pulled the rear cover off the differential. Soaked the drain and fill plugs with Kroil for a day. Then put the cover in a vise (with wood blocks), applied a little heat from a propane torch to both the inside and outside surfaces around the fill then drain plugs. They broke free pretty easily at that point.

Inspected the internals of the rear end, replaced the gasket and cover, then coated the plugs with anti-seize compound. Steel plugs in an aluminum cover always call for anti-seize compound.

FWIW,

Carl B.