Duster 360 is right about how to tighten the pinion, his methed for taking the slop out is exactly what I do the pinion can't move in and out anymore it also takes the side to side slop out of the pinion as well. Just remember not to put to much pressure on the pinion and drive cup when you tighten it or it will start to bind the bearings a little. If you don't use a good threadlocker on the set screw it will come loose and you will have to take everything apart again and do it over.