Diff whine

[Stevesas12]

As I'm new & never driven a 1m before, is it normal to have slight whine or hum at cruising speeds while on throttle? Come off throttle stops, back on is there. Go over a certain speed also goes.
My last car, an EVO 8 did this exact thing after I changed diff bush mountings for poly ones, although was more noticeable than the 1m.
Should they be completely quiet at any cruising speeds? Diff oil changed by BMW dealer in August & car on 24k miles.

Thanks

[CarJunkie]

My diff is quiet, even before a recent gear oil change....oil was definitely bad and losing viscosity. Consider changing the fluid.

That could also be a wheel bearing....does it change when turning one way or the other?

[nachob]

Originally Posted by CarJunkie

My diff is quiet, even before a recent gear oil change....oil was definitely bad and losing viscosity. Consider changing the fluid.

That could also be a wheel bearing....does it change when turning one way or the other?

I hear lot of sounds but not diff. There was a cv joint recall on some 1Ms if I recall or the diff might be making some noise perhaps. Too hard to tell without listening. It's pretty easy to check the guibo and diff bearing. Because you said it happens when you apply power I don't think that's a wheel bearing but perhaps a diff, gearbox or driveshaft. Others sounds would happen even if not applying power like bearings or separates tire belts

[CarJunkie]

Originally Posted by nachob

I hear lot of sounds but not diff. There was a cv joint recall on some 1Ms if I recall or the diff might be making some noise perhaps. Too hard to tell without listening. It's pretty easy to check the guibo and diff bearing. Because you said it happens when you apply power I don't think that's a wheel bearing but perhaps a diff, gearbox or driveshaft. Others sounds would happen even if not applying power like bearings or separates tire belts

I recently replaced the rear wheel bearings on my e30. When they first start to fail, they are only noisy when loaded. Initially I only heard noise when accelerating. I could have sworn it was the diff. The right was worse, so it eventually became more noticeable when turning left, which would load the right side.

[godzilla-1]

I'm pretty sure that I went back to main dealer a few years back for a recall on the propshaft bush. Maybe yours is still the original. I didn't notice any noises but I run on R888s which make a fair bit of noise so I can't really comment.

[Stevesas12]

Cheers everyone for the reply's, I know hard to determine without investigating.
Next dry day I'm off, I will get up on ramps, have a good visual look, for any play, leaks or even uprated bushes etc. I know there is an H&R ARB on the front, so you never know. If I don't find anything obvious, I'll check the diff fluid level while I'm there.
I also have handbrake to adjust while I'm under there.
I need to get someone else with a 1m to drive it, to give an opinion.
I will get along to a local BM specialist to see if they can run it up in the air & determine where noise coming from.

[Stevesas12]

Hi guys,

so upon further investigation the rear also have uprated ARB (H&R) & I'm pretty sure the diff mounts are non OEM as well.
The bushes are black, but definitely poly material so probably Powerflex Black series.
The slight whine (more a faint hum) on light throttle & cruising speeds (50-70mph) is so similar to the one I had on my EVO 8 after the diff bushes were replaced with Superpro purple ones, that I'm pretty sure its the cause.

[CarJunkie]

Originally Posted by Stevesas12

Hi guys,

so upon further investigation the rear also have uprated ARB (H&R) & I'm pretty sure the diff mounts are non OEM as well.
The bushes are black, but definitely poly material so probably Powerflex Black series.
The slight whine (more a faint hum) on light throttle & cruising speeds (50-70mph) is so similar to the one I had on my EVO 8 after the diff bushes were replaced with Superpro purple ones, that I'm pretty sure its the cause.

Interesting. Makes sense. Harder bushings and solid mounts definitely increase NVH.

I recently upgraded motor mounts to ADE, and you can feel the engine at idle. Stock idle speed (650rpm) was ridiculous so I turned the idle up in MHD. At 900 rpm it is still noticeable, but actually cool. It has an "Its ALIVE!" effect rather than a "WTF is wrong with this car" effect, LOL.

[aaronwilliam]

Originally Posted by CarJunkie

My diff is quiet, even before a recent gear oil change....oil was definitely bad and losing viscosity. Consider changing the fluid.

That could also be a wheel bearing....does it change when turning one way or the other?

Right, improper gear set up and oil is the reason number one but worn ring or carrier bearings may also be the cause.

https://theessayservice.org

[Osiris]

Originally Posted by aaronwilliam

Right, improper gear set up and oil is the reason number one but worn ring or carrier bearings may also be the cause.

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I had that problem. You need to change the diff oil. You have to use this one with booster not the one with out. Then it will go away.

[Osiris]

Originally Posted by Osiris

I had that problem. You need to change the diff oil. You have to use this one with booster not the one with out. Then it will go away.

This was a pain for me as well. I changed the oil a few times until I PMed Dackel (RIP). He was the one who told me this trick. Use SAF-XJ+FM (friction modifier) NOT SAF-XJ which most dealers and shops use.