okay so most people have trouble with this and ill make this so easy i wont even need pics.okay first take aprt the back of the xmod and take out the gear,the big one in the middle,look at the side of it,but first take off the bearings.duh.there should be 3 tiny holes on the side of it,only one side though,just take tiny pices of paer and jam them in all 3 holes.and then put the car back together.and there you have a lockked diff.this goes the same way with the freont if you want a locked front diff but only lock the front if you want to drift because otherwise it just makes the car run worse.