Here is a link on how to build your diffs and seal them best as possible:
http://www.team-durango.com/blog/?p=24
Instead of the green slime i use waterproof grease which can be bought here:
http://marinestore.co.uk/Merchant2/m...ls-and-greases
I can race my car for weeks on end after using this stuff without having to refill the diffs.