Are you sure your X doesn't already have an LSD? Slide under the rear and look for a sticker on the Diff saying 'LSD Oil Only' (Or something along those lines).

I believe the LSD in the 2000 and 2001 X's had a much better break stength than the 02 onwards. 200lbs compared to 30lbs. The LSD in the 2002 onwards therefore being pretty useless really.

Just traded my 2000 LSD equiped 2WD for a Locked 4x4 tho, so I shouldn't have any problems getting up and over stuff anymore!