Just how many pumps from a grease gun do the front axels hold

I just keep pumping until it oozes out the seals a bit.

Rich is correct in his recommendation to grease until some comes out.

If the joint that you are greasing has seals that can relieve without damaging the seal, part of the function of regular greasing is to clear old grease and debris from the joint and seal.

This is from the Dana Corp. On greasing universal joints.

Important:  Properly purging u-joint lubricant during vehicle preventative maintenance service is critical to ensure long service life of the vehicle driveline components. Proper lube purging is evident by fresh grease exiting all four bearing cup seals (white arrows) when grease pressure is applied to the u-joint grease zerk fitting. This procedure will replenish the bearing cups with fresh grease, while pushing contaminants and air pockets out of the u-joint. Failure to properly purge the u-joint can cause premature failure and possible driveshaft exiting from the vehicle.

Cheers

Jim B