8 3/4 axle lube change

I'd recommend removing and cleaning the vent found in the brass distribution block the brake lines go through. Should be bolted on top of the driver side housing. I'd also change the oil if you don't know how long it's been in there. An easy way to drain it completely is loosen the bolts holding the center section and use a jack to press up on the pinion yoke. That will crack it open enough to drain and it should re-seal by just tightening it up again if the gasket is not damaged. I've done three like this and never had a leak afterwards.