When I had my quaife installed (also some time after installing leader gears) the shop had to reshim and set the lash to get the gears to mesh correctly. In theory the quaife unit should just drop in place of the factory lsd without moving the alignment of the gears but that was not the case with my unit. There has since been a recall of the quaife units which may rectify this problem. The main problem which the recall was in relation to was that the hub was too big to fit the crown wheel on. The diff shop I used had to machine 30 thou off the hub to make the crown wheel go on. They also recommended a 1000km oil change after run in.