I did a write up with pictures on how to do it....look in the faq/diy section and look for the thread DIY Front End

 

replacing those seals is not a good starter project.
see here.
http://www.pavementsucks.com/tech-article-3.html
http://www.pavementsucks.com/tech-article-5.html

this is my recommendation. buy a quart of 90W gear lube and top off your front diff. monitor the leak and see how bad it is. refill accordingly.
also do this... after one or two refills, intentionally underfill it an inch or two which will leak less and then monitor that for awhile.

see how bad it really is and procrastinate some.
i let mine go for a year or two before tackling the job when it needed axle U-joints.

 

I just topped off the front diff. It needed about a 1/4 quart. I cleaned up the leak area so I could see how bad it is. I'm going to need to procrastinate, hopefully until spring when I can buy a compressor.

How is the leak going to effect my use of 4-wheel?

 

The leaking seal will not effect the use of 4wd, but the use of 4wd might effect the seal 50/50 call. Watcha need a comp for? This job can be done without one, and I would do it before the wet/cold winter gets here. Cold will not help the seal one bit, probably make it worse.

 

+1... And I say the reason the seal is bad is most likely because the ujoint is vibrating, or hub bearing for that matter.

 

Thank you everyone, HUGE help. I'm learning a lot.

 

Just be glad that yours is somewhat of an easy fix. My whole front end is basically blown right now so I just pulled my d shaft and left it be until I can get my bosses old axles out if his truck. But seals aren't all that easy and yes you can use hand tools. The axle nut is an 1-11/16 size socket btw cause I just did u joints in mine only to find out my pinion bearing is blown and that seal is leaking. But oh well. If you did do it you can get one of your buddies to hold the hub with a pry bar on the studs and get a breaker bar for the nut and it will come out.

 

here's a tip if you can't get the big axle nut off and you don't have an impact wrench.

take your socket and drive to a local tire shop and have them remove the big nut with their impact wrench. oil it up good and reinstall by hand/pullbar to an undertorqued amount of about 150-160 pounds. DO install a cotter pin. drive directly home and take it apart.