[17F25X3]

Hi, recently a strange noise has been occurring when accelerating passed 20MPH, it sounds like a winding up noise (sounds very electronic sounds like its coming from the front). It only gets louder at higher speeds, and when slowing down or letting off the gas pedal the noise softens.

My car is a '17 F25, with just under 50k miles on it, the noise began less than 3k miles ago but was not as loud.

I seen other posts that say it could be a belt or AC comp, but mechanic says that's okay.

Had it looked at but mechanic, believes its a rear differential problem (found metallic shavings in the RD oil). I don't argue that I will possibly need to gets the RD changed.

Can the RD be making such noise?

[x3aniac]

Yes. I have same type of thing you’re describing. Look at my post here: https://x3.xbimmers.com/forums/showthread.php?t=1980364

[Opie55]

Let us know if your rear diff fixes it. My sound described in the linked thread sounds distinctly as if it's from the rear, not the front, like a tiny airplane following close behind me.

[Spoolin335i]

Our 16 xdrive35 made the same noise and at the same conditions. Drove me nuts. Thought it was the diff since making left or right turns made no difference. Found out it was both rear wheel bearings. Been two years and the noise never came back. It happened at around 42k miles. EXACT symptoms and at the exact conditions.

[Opie55]

Originally Posted by Spoolin335i

Our 16 xdrive35 made the same noise and at the same conditions. Drove me nuts. Thought it was the diff since making left or right turns made no difference. Found out it was both rear wheel bearings. Been two years and the noise never came back. It happened at around 42k miles. EXACT symptoms and at the exact conditions.

Can you be more specific on the sound you had? The OP said his sounded like an electronic sound coming from the front. Did yours sound like it was from the front, or distinctly from the rear? And can you say what it sounded like in your own words, because "electronic" creates an image of high-pitched to me.

[Spoolin335i]

Originally Posted by Opie55

Can you be more specific on the sound you had? The OP said his sounded like an electronic sound coming from the front. Did yours sound like it was from the front, or distinctly from the rear? And can you say what it sounded like in your own words, because "electronic" creates an image of high-pitched to me.

Sure. So it took about a year before I had it repaired. The noise was there for a good year. I mostly drive the x3 now so being in the driver seat, the noise sounded like it came front the front, the bottom center, and the rear! So at first I thought it was the diffs or transfer case. It sounded like a low humming, like growling noise that only happens above 20mph and gets louder as you speed up. Low speeds, think of a cat that growls. Popping it in neutral while driving didn’t change the pitch or the noise. It was constant. Make sharp turns at any speed didn’t change the pitch also. When finally I sat in the back seat, the noise was louder coming from the back and I for sure thought it was the rear diffs. I used to be a master tech for BMW and I enjoyed the hunt for it, but I didn’t have anyone else to help me isolate the noise when I jacked it up. Finally brought it to my friends bmw Indy shop. When they lifted it, both rear wheels were humming and it was LOUD. I have a video of it that they sent. After replacing both, sound is gone for almost 2 years now.