[isorock]

Car: 2022 Z4 (G29) [Sdrive30i]
Mileage: 11000
Driving mode: Sports mode
Transmission: Automatic
Unmodified, no accidents

This has happened twice this month, and it happens when I'm driving on the road (will describe exact conditions after problem description). The sound doesn't start immediately when I start driving, but rather a few minutes in. The sound is barely audible with the windows rolled up, but if I roll the windows down it's quite an audible sharp grinding/whirling sound. The sound is intermittent (a few beats a second) and the intensity increases as I go faster (15mph up to 40-50mph). This would happen for a few minutes (as I accelerate and decelerate to characterize the sound). For both times, when I was driving at around 40mph, there would be an audible hissing sound which lasts for about 1-2 seconds sounds like air venting, after which the grinding/whirling sound would go away.

The first occurrence was when I was driving a short distance from my home (5 minutes on the highway, after exiting). When I noticed the grinding sound I slowed down/sped up to see if the sound changes in intensity (it does), and after about 2-3 minutes of driving I heard the hiss and the grinding sound went away. I drove back home (5 minutes back) with no incidents. After this I've driven the car a few more times (one 1-hour highway trip and a few 5-10 minute local trips) with no issue.

The second time it's happened was a week after the first incident, I backed out of my home and got onto the local road, about 2-3 minutes into the drive the grinding sound started, with the same behavior (a few minutes of the grinding sound that goes away after the hissing sound).

I've taken the car to an independent car service as well as the dealership for an inspection, but they said the car looks fine and there's no issue. They told me they checked underneath the car and nothing is stuck on the axles, and the sensors did not show any errors. This sound is a bit worrisome, can anyone help me diagnose the issue?

[Balr14]

The next time, try changing modes, or shifting with the paddles. With no error codes and no active symptoms, you have nothing to go on.

[Westside Guy]

Originally Posted by isorock

I've taken the car to an independent car service as well as the dealership for an inspection, but they said the car looks fine and there's no issue. They told me they checked underneath the car and nothing is stuck on the axles, and the sensors did not show any errors. This sound is a bit worrisome, can anyone help me diagnose the issue?

IMHO, just looking underneath the car and checking the sensors isn't enough and you shouldn't accept that type of answer. Definitely go for a road test along with the dealer's SA (don't let him do it alone). Back out of a parking space and try to recreate what occurred the second time when you heard this grinding noise.

[z4monster]

That could be a stone getting lodged in the brake shield. From your description of the noise, I've had similar before and once the stone dislodges, the noise stops. Varying with speed gives a good clue. The hissing noise could just be it moving and then falling out.

[StanDiego]

Originally Posted by z4monster

That could be a stone getting lodged in the brake shield. From your description of the noise, I've had similar before and once the stone dislodges, the noise stops. Varying with speed gives a good clue. The hissing noise could just be it moving and then falling out.

+1

[StanDiego]

Originally Posted by isorock

Car: 2022 Z4 (G29) [Sdrive30i]
Mileage: 11000
Driving mode: Sports mode
Transmission: Automatic
Unmodified, no accidents

I've taken the car to an independent car service as well as the dealership for an inspection, but they said the car looks fine and there's no issue. They told me they checked underneath the car and nothing is stuck on the axles, and the sensors did not show any errors. This sound is a bit worrisome, can anyone help me diagnose the issue?

I just read a post on FB, guy had grinding noise on his '19 s30i, diagnosed as bad differential, backordered from Germany. It's the first I've heard of a G29 differential failure. I hope this isn't what's wrong with yours.

[RavenGX]

Originally Posted by StanDiego

I just read a post on FB, guy had grinding noise on his '19 s30i, diagnosed as bad differential, backordered from Germany. It's the first I've heard of a G29 differential failure. I hope this isn't what's wrong with yours.

Attachment 3377463

i know someone else who had to replace his diff.
His was a tuned car, so they blamed it on the tuning. He had to pay for the entire repair himself. It was also making "noise" he said.

Another good reason to have a loud exhaust, if you don't hear it, it's not a problem

[MisanoblueZ4]

Originally Posted by RavenGX

i know someone else who had to replace his diff.
His was a tuned car, so they blamed it on the tuning. He had to pay for the entire repair himself. It was also making "noise" he said.

Another good reason to have a loud exhaust, if you don't hear it, it's not a problem

Differential noise/grinding was common on C6 Corvettes when making tight turns.

I had it happen on both my former C6’s…..fix was to drain diff fluid and refill, then perform figure 8 turns in a parking lot to work in the new fluid. Worked both times and never heard noise again on either car.

Not sure of our M-diffs are serviced periodically but if anyone hears noise a fluid drain and refill should be first step.

[misterturbo]

Was going to say wheel bearing, but I did test drive a 2020 30i with the same issue you experienced. This one had the LSD option though.

In general, differential issues across all cars are pretty rare. I’m a bit surprised they went straight to a replacement rather than diagnose and repair. Maybe they know something we don’t?

[StanDiego]

Originally Posted by isorock

Car: 2022 Z4 (G29) [Sdrive30i]
Mileage: 11000
Driving mode: Sports mode
Transmission: Automatic
Unmodified, no accidents

I've taken the car to an independent car service as well as the dealership for an inspection, but they said the car looks fine and there's no issue. They told me they checked underneath the car and nothing is stuck on the axles, and the sensors did not show any errors. This sound is a bit worrisome, can anyone help me diagnose the issue?

Hopefully we'll get an update from you when the issue is identified and resolved.