Loud hum from what?

[xLibelle]

So i have a 4.10 LSD thats estimated at about 80k miles and the rest of the drive line is over 200k. Azenis tires at proper inflation (ive tried other pressures to see if it was the tires) and increased camber from lowering.

Almost positive its the diff but the sound varies day to day. Sometimes its quiet and others its insanely loud. so it could be bearings. Obviously speed based and can change slightly from various amounts of torque.

Video taken on fresh asphalt and its hard to distinguish unless you are really familiar with m20's because you can hear it in the background to help define the difference between typical road noise and the whine/hum from the rear end.

Serious to help only, please. (save as)
longer version available but i dont think you'll get much more
there are no loud sounds so its safe to crank volume

[cferb]

Dumb question, but have you checked the tranny and diff fluids?

[lordofthewaters]

Couldn't really hear much humming, but I can get my sound to loud either. What I could hear is sounding to me like maybe a wheel bearing or csb.

[xLibelle]

not a dumb question - fluids are recently (within 5k) refilled with redline products.
Also to note, i have not noticed any wheel bearing movement to show the sign of that being worn.

i suppose ultimately i'll have to throw some parts at it to really fix it. Just thought someone knew the sound (as bad of a recording as it is) first hand.

Keep suggestions coming. Thanks everyone


on a side note, anyone know a way to check how "good" a diff's clutch is?

[xLibelle]

lol, just listened to it at work... man thats loud. deffinetly not right

[E30nate]

mine is making the same sound. im pretty sure its the diff. have you checked your cv shafts. they could make a humming sound if there is no grease in them.

[xLibelle]

mine is making the same sound. im pretty sure its the diff. have you checked your cv shafts. they could make a humming sound if there is no grease in them.

interesting. something to pay attention to when i get a new diff in there.
how about you, grease in yours?

[kenika65]

Throw it on jack stand and put the car in drive then get under there with a stethoscope and you will find your hum in no time...

[E30nate]

interesting. something to pay attention to when i get a new diff in there.
how about you, grease in yours?

no grease in one of mine, the boot tore. when i go around corners the noise gets louder, but only around right hand turns.

[jekaio]

if you need an extra set of ears i could possibly help you out.

[xLibelle]

you in charleston? good at turning a wrench?

[jekaio]

yea im in west ashley.

ive turned a couple wrenches in my day.

[///M42 sport]

i've got same sound.

[gearheadE30]

Note that I havn't seen the vid yet.

I'm going to take a guess that that is not the CV joints. When CV joints wear, they rattle and click. I've never heard a bad CV joint hum before. The bearings in these diffs, especially the input bearing, can make a good amount of noise as well. My bet, though, is that it is wheel bearings. 200k seems to be about the failure point for them.

I'll edit this after I watch the video.

[///M42 sport]

I was about to change out my rear wheel bearing until I saw my cv boot was torn. I guess its back to the dealer tommorrow. I'm not sure if its the wheel bearing or the torn boot w no grease. My wheel bearing is only a couple years old.