I recently added some higher durometer diff. bushings and immediately noticed a whine noise from the rear end at certain rpms while at criuse. Most noticeably below 3000 rpms in 4th and 5th gear and at slight on and off throttling. Pretty much when the rearend has a load shifted to or from. I went on a trip w/ some spirited driving and started to get worse. Thought most definately the cause was the bushings. Well I swapped those out for some mazdaspeed liquid filled ones ( just abit more stiff than stock) and the problem is still there. My suspension mods are tein flex coilovers, noltec motor mounts, banzai diff brace and the diff. bushings. Before making any suggestions I have taken the diff. brace off w/ same result. Also I added each susp. mod 1 at a time and zero whine until the diff. mounts. I am now thinking a possible wheel bearing? Thanks G

 

I went out tonight and beat the **** out the car. Wanted to see if the mazdaspeed bushings would have added a bit of wheel hop back into the equation because they are liquid filled like stock but rated harder. They actually feel very good. I had my coilovers at full hard as well. The whine is def. still there. Especially on the highway . Looks like I am goind to need a diff. I cant see what else it could be. The car feels great just aggravating sound. G

 

You can change the diff oil and see if there is metal in the old oil.

Dave

 

Yes. I suppose. I just did a fluid change a couple thousand miles ago w/ Neo synthetic. It looked good then. That was before the noise though. Guess I'll drain and look. G