Originally Posted by c4s335i
$4k sounds a bit much for a differential. The stock m3 lsd diff is under $2k, and it's a clutch type.
He's probably factoring in install price. The $2k~ M3 differential will require modification of the driveshaft, which will jack up the price more.
+1 for Harold! Bought my Quaife though him and loving it ever since. There is no other vendor on here I'd trust with suspension upgrades.