What Gear oil do I need for a 73 RR

[Barry_Calgary]

Hi All,
What type of gear oil do I need for my 73 Roadrunner? and how do you change it?
I have had the car a few years now and thought being that I don't know the maintenance history I should probably change it.
Any recommendations appreciated.
Thanks

 

[PurpleBeeper]

You almost can't go wrong with gear oil. Stock is probably a 75W-90 or something close to that weight. In a colder climate like Canada, the thicker stuff (75W-140'ish) might get too thick. If you have a posi/limited-slip rear end, it's important that you add "posi additive" or use gear lube that already has it in there.

To drain the old stuff, either remove a lower pipe plug or remove the rear cover depending on what rear end you have. Most have a cover, but 8-3/4" does not. Scrape off the old gasket, use some spray tack to hold a new gasket in place & bolt the rear cover back on. Finally, remove the pipe plug in the cover (or upper pipe plug on 8-3/4" rear end), pour in your posi additive (if appropriate) and fill up to the bottom of the pipe plug hole with gear lube. The hole is the "full" mark.

A really good idea is to get a "gear lube hand pump" at a local auto parts store. They cost about $15 and look like a baseball park ketchup dispenser pump with some plastic hoses. You pour 3-4 quarts of gear lube into an empty antifreeze bottle & use this pump to squirt the gear lube up hill into the pipe plug gear lube fill hole. This tool is worth its weight in gold!