Diff vibration/noise on decel
 

see if anyone has any advice. a little back round info. Im running a OSG LSD in an M85 housing using 3.73 gears also white lines diff bushings and DSS axles (noise was happening before axles) ,the side bearings are new like 3k on them the diff had 43k out of a wreaked Lexus. using OSG fluid.
so when i let off the throttle in 5th there is a noise coming from the diff like vibration or a hum. but its only in 5th and only on when you let off the throttle. doesn't do it any other time.

Could it be happening in other gears and you're just not hearing it? If it's all the gears, maybe the backlash is off. If it's just 5th, that would make me think it's a transmission gear issue, since that's the only place where 5th limits movement to a specific set of gears.

im fairly certain its only in 5th. cant be 100%. that is the part the is confusing me.i thought it might be a transmission issue but it started right after i did the diff and engine mounts. backlash should be good i checked it before i installed and the pinion depth never changed.

The diff outrigger bushings definitely amplify gear whine a bit, so that's probably it. I get it in 1st and 2nd when I coast in gear at low speeds. Otherwise my radio is too loud for me to hear it anyways. Some people leave the back bushings on and remove the front outrigger bushings; they say that seems to help. I just live with it, because it isn't really annoying to me.

Its your bushings and mounts, forget you think you even have a problem.

If it's normal why only in 5th ? My only thinking is it has something to do with it being 1 to 1 ratio

I would look at the trans not the diff if the only time it does it is in 5th. also you might want to try swapping diffs back to make sure its the diff.

I bet it's the whitline diff bushings...mine make similar noises in 5th.

+1

The midshaft does not have its own thrust bearings. It relies on a balance of opposing axial forces between the input and output gear pairs.

If either of the end bearings is shot, I can picture the midshaft rattling around in fifth gear while it's unloaded.

Credit to @VeloxEric for sharing his experience.

That makes sence I figured my transmission will not last me through this season of racing anyway. So I will find out one way or another.