Rear drive axle lube capacity for 1983 Chev Malibu

In reality you would need to know if the diff is original and if it is a "12 bolt" or "10 bolt" unit. Gear lube is not terribly expensive. I recommend you just follow correct fill procedure, adding lube while vehicle is resting on flat ground, and filling 'till lube just begins to spill from the fill hole. On most, this is generally close to or a bit more than four quarts. If you buy in quart containers, simply return whatever you did not open..