I have had 3.91s in 741 case set upn and all new bearings and there is still some noise that is ring and pinion related. I have a set 4.30s and 4.56s in 489 cases and they are quiet. I'm convinced once they have a pattern set you will never get rid of all the noise. I can say the noise is ther but they have survived so far 1 year and several dozen hard passes with M&H's.