I fitted a NoSlip to the rear of my XJ and the thing didn't work properly. It was definitely the right type for the diff fitted but it used to go bang and lose all drive without any warning. I never got it sorted and took it out again. I could only put it down to the carrier being worn (245000 miles) so the two halves of the Noslip assembly were a bit too far apart resulting in the strange behavior. It always checked out alright when testing it on jacks but wouldn't work properly when driving. I refitted it twice and contracted the manufacturer but without seeing it assembled in the diff they couldn't help me further so I gave up and sold it. I also had problems with one in my YJ, this one was definitely down to carrier wear.