What's the best way to remove the axle housing seal from an 8 3/4 housing? Is there a specific tool for this?

As you slide the axle out hole the flanged end towards the rear of the car and slide the splined end against the inside of the housing till it hits the seal and pry rearward with the axle and the seal will come out on the end of the axle. No special tools needed. It may not work for you the first time but it is a very simple way to take out the seal and it is done all in the same operation as removing the axle.
Remember to repack the axle bearing with a good wheel bearing compatable grease as this is the only lubrication it gets. It is not lubricated from the rear end lubricant.

if the brake assy wont let you get the just the right angle to catch it & it doesn't for me unless the backing plate & everything is off of there,easiest is to use a piece of allthread as a slide hammer & heat up & bend an L on the other end

Never had a problem even with the brake shoes in place. It doesn't take that much of a pry to release the seal. been doing it this way for years now.

I used a long broom handle. Put the handle in from the opposite side and place it against the back of the seal and hit it will a hammer. Of course the pumpkin was removed.

Yeah I've heard forever that the seals will pop out almost by themselves with the end of the axle to pry them but not for me unless the housing end is stripped. Maybe my skill level isn't as high as I think it is .

My luck has been 50/50 on getting them out with the axle. There is a seal removal tool that will work. Not one of the pry bars with the like half moon shaped ends. I actually got mine at harbor freight. Small bar with a hook on the end of it to catch the seal. Then a square bar welded at a right angle on the bar. Smack it with a hammer and it will pop right out.

I use a cheap slide hammer with the "L" shaped attachment. Due to the depth the seal sits in the axle tube it's difficult to get the new seal in and seated properly without a seal driver imo. So buy extra seals just in case.

For those who have never seen one.

Remember also when you drive the new seal in to drive it in till it hit the solid lip in the housing as a stop.