[Doenermann]

This is a fun one. US Car at dealer for 2+ weeks, corporate technicians involved, and they suggest an expensive repair 'next step' with no Guarantees. But first things first - 2018 530e xdrive, 56k miles, standard m sport suspension and 19" factory wheels (checked and one freshly straightened) on new Michelin PS4 AS (non-rft). I was luckily to find a shop foreman at the local dealer who really wanted to help and is keeping me in the loop on all the trouble shooting steps. Not my normal BMW service experience but very thankfully since I'm out of factory warranty. Here's what's happened so far:

Vibration and humming noise starts at exactly 69/70 mph, and stops again completely below 67/68 mph. Shop foreman drove with me and heard the noise, felt a vibration.

Steps taken by shop foreman:

- despite alignment and RF balancing, checked rims and straightened a slightly bend rim per his recommendation - no change

- swapped rims and tires from his personal Car ('18 540 x drive) onto mine, smooth on his car - no change on mine

- he started thinking what might be unique to the hybrid - change in charging behavior at that speed, other issues… he disconnected the front drive shafts electronically thinking that that could be the issue - test drive as rwd - no change

- filed ticket with BMW NA, but kept pondering e drive specific issues. He found that the active motor mounts are programmed to change (something, not sure) right around 70mph. He suggested that to BMW corporate - no reply

- they had him load the car with 5 adults (technicians) and drive it, all confirmed the noise and slight vibration, then they had him check front and rear diff fluid - front was black, smelled (have photo) rear looked normal, less smell. Still no reply from corporate on the mounts (speed changing behavior at 70mph just coincidence?), but they did say a new front differential is next trouble shooting step. A costly step…

I do have a third party warranty purchased from a dealer that should cover most of that very pricey repair, but not all. Could the diff really be the issue? Should new motor mounts be done as well? He said the mounts weren't leaking with vacuum lines disconnect so most likely fine. He honestly doesn't know if this will fix it but he does agree with corporate that the fluid should have looked better after 56k miles.

If anyone has any experience or input to share regarding a front diff and vibration, motor mounts and vibration (someone else had that issue on an F gen car), or any other suggestions please let me know.

Thanks!!

[CnSky]

It's you MPS4 tyres they are not compatible with G30 cause rhythmic humming at highway motor speeds check my previous posts.

I proved this beyond doubt using vibration analysis software and two sets of tyres.

I'd say ask them to swap wheels with another new car on the lot with star marked tyres and see if it goes way,

Also this could be a badly programmed ACSM or VDP if you have adaptive dampers or even in your case where you don't a bad ACSM messes up all sorts of stuff as it manages all sensor data. (Easy to blank them and recode but BMW won't do that, you need an Indy who can do it remotely this won't affect affect your warranty,I can list people in here who can do it for $100)

Search my previous posts sounds very similar took me 8 months by myself to fix and BMW couldn't figure it out.

Also ignore variable mounts they go hard at 1500 rpm not high speed this is to handle the stop start of the engine.

[turbobeagle]

Originally Posted by CnSky

It's you MPS4 tyres they are not compatible with G30 cause rhythmic humming at highway motor speeds check my previous posts.

I proved this beyond doubt using vibration analysis software and two sets of tyres.

I'd say ask them to swap wheels with another new car on the lot with star marked tyres and see if it goes way,

Also this could be a badly programmed ACSM or VDP if you have adaptive dampers or even in your case where you don't a bad ACSM messes up all sorts of stuff as it manages all sensor data. (Easy to blank them and recode but BMW won't do that, you need an Indy who can do it remotely this won't affect affect your warranty,I can list people in here who can do it for $100)

Search my previous posts sounds very similar took me 8 months by myself to fix and BMW couldn't figure it out.

Also ignore variable mounts they go hard at 1500 rpm not high speed this is to handle the stop start of the engine.

Just to confirm - are you referring to the summer or all season version? I have the all season (Michelin Pilot Sport All Season 4) like OP and don’t have any issues.

[CnSky]

It's hit and miss some people say they are ok other not. Size is a factor 20s more likely to show issues.

Multiple people on here reporting the problem.

Seems to affect Michelin tyres (sport and AS) that are not star marked. Non star marked Michelin tyres are actually manufactured different steel bands are different and it can cause major issues.

In my case Michelin agreed and refunded when is showed them the evidence.

But in the OP case it sound like he should first have his ACSM blanked and recoded and not 100 bucks bet it's the problem as it kicks no fault but as the ACSM controls flex ray and all sensor signals ant issue can cause major problems for diffs, gearbox and if fitted variable dampers or air suspension for g31.