Humming/Whine under slow acceleration

[nicknick118]

F80 M3 whine / humming at low speed

Recently bought an F80 M3 2016 which intially had no sounds or anything coming from it. The car drives mechanically sound.

A week ago I had noticed that I have this deep low pitched humming/ whine sound coming in at slow acceleration between 18-30km/hr in 2nd gear. When accelerating and letting the foot off the throttle or hearing it specifically when holding the car at 18km/hr. I had changed the diff fluid 2 days ago and the sound is still there. Used bmw 75w-140 diff fluid.

Any info would be much appreciated

[rmanm4]

Could be bearings.

Put front of car up and spin each wheel by hand and see if you hear bearing noise.

The rear is a bit harder to diagnose if wheel bearings are the issue and which side.

[Luski]

I have the same noise, goes up and down with rpm. I also slightly hear it when revving at standstill in neutral. Got my 2017 less than a month ago so also not sure what the sound is. Commenting to see if others know.

[imbrzyant]

My 17’ Comp does this too. It’s totally normal. I think it’s the noise coming from
the diff.

[nicknick118]

imbrzyant Hard to know due to mixed opinions. Some say it’s not normal some say it’s normal 😅

[Luski]

Hey just wanted to give an update. Took my car to get inspected by BMW. My diff is leaking at the pinion and whining as well at a couple different points. Got quoted for a new diff assembly including driveshaft. I’m under warranty with carmax so it’s being handled, but wanted to let you know what the cause was in my scenario!

[nicknick118]

Luski Has the work been carried out ? Is it still making that noise ? What exactly has been changed ?

[Luski]

Originally Posted by nicknick118

Luski Has the work been carried out ? Is it still making that noise ? What exactly has been changed ?

Hey, not yet - got the car diagnosed last week by BMW but since I’m still within 90 days of purchase from carmax, I have to take it to them to fix. Taking it this Wednesday so I’ll keep you updated. Parts list from BMW is the full differential assembly + driveshaft, not sure if seals would have just fixed it but BMW repair procedure replaces the whole thing I assume

[nicknick118]

Luski Did you get the job done in the end ?

[Luski]

Originally Posted by nicknick118

Luski Did you get the job done in the end ?

Hey! Sorry for the delay, car was sitting in the shop for the past 2 weeks waiting lol. But yes got the full rear diff replaced. Still have a small whine, not nearly as loud as before so I think it’s just normal, and it is much smoother now than before.

[Lehman]

It's the same on my '17 comp. There's a weird whining noise when accelerating at low rpms, specifically around 50-60 km/h. However, you can only hear it in efficient mode, so I just put it in sport or sport plus immediately nowadays, problem fixed

In all seriousness it's nothing to worry about. As others have said it's probably the diff, any money thrown at this "problem" will be a waste.