High speed humming and vibration, loud squeal at redline
i just purchased a 2014 E550 4Matic that’s been CPO’d. On the long drive home (8 hours) I started to notice a few things as I played with the vehicle. I did a search on these and couldn’t find anything so hoping others out there have experienced the same issues. Find it odd that it’s CPO’d and these were not caught before.
1. Between 85-95 MPH, you can hear a quite audible hum coming from the front of the car. It’s only while cruising with minimal throttle input. When I add more throttle response—when I hear the exhaust specifically—the sound goes away.
2. Also starting at 90MPH, the car tends to vibrate quite a bit. Not to the point of unsafe behavior, but noticeable enough to annoy you!
3. I just noticed this today while giving a friend a ride. Sometimes in 2nd gear very close to redline, a loud whining noise—like a supercharger—occurs for a second before the upshift occurs.
Anyone ever heard of these issues? Other than these, this car is great!!




normally I’d just say likely balance issue possibly tires as well, and very well could be. But on these cars, you can’t ignore the rims as easily as on other cars. I have a 15 VW GTI as well, 18 inch wheels low profile tires. Those are forged wheels, never a problem.
depending where you live, likely a few places that can fix them for maybe $150 per wheel if that much. Dealer can fix it too, but if given excuse of wheels not covered by CPO warranty (they may not) you don’t have to pay dealer prices for the fix. They just hire out to a wheel company locally who typically has a few dealerships on their client list. Just go direct and avoid the dealer tag-on markup.
Last edited by nc211; Jun 27, 2018 at 07:08 AM.
The vibrations have now increased to pretty much all the time. The ride used to be super smooth on our road—paved only a few months ago. Now you can feel just about everything while even at low speeds.
A few few more things have popped up in the process too:
- Vibration while accelerating, deceleration and braking at any speed really.
- Now car lunges when going into drive, reverse and especially park—used to not ever feels this.
- Sputters while in neutral, park and consistent throttle while driving (you can see the tac move too)
- Ac is fluctuating
I purchased the car unfortunately 500 miles away, so taking it back to the dealer is very impractical. But, I’ll be taking it to my local dealer after chatting with the place I purchased it from. Really hoping that everything will be found...
- driveshaft issue
- engine and/or transmission mounts collapsed
- front or rear diff bearing issue
I'm not so sure about a bad pulley but maybe it can contribute in addition to another issue.
Please post results of your dealer visit, I'm sure it will help both 350 and 550 owners alike. I hope it turns out to be minor trouble.
Agree on just going directly to wheel repair shop if it's a rim. I went to the same place the dealer uses. $150 per rim included straightening as well as prep and powdercoating to a different color.
Last edited by Mud; Jun 28, 2018 at 09:59 PM.
- driveshaft issue
- engine and/or transmission mounts collapsed
- front or rear diff bearing issue
I'm not so sure about a bad pulley but maybe it can contribute in addition to another issue.
Please post results of your dealer visit, I'm sure it will help both 350 and 550 owners alike. I hope it turns out to be minor trouble.
Agree on just going directly to wheel repair shop if it's a rim. I went to the same place the dealer uses. $150 per rim included straightening as well as prep and powdercoating to a different color.
Ill definitely be making updates as they come. I’ll be dropping the car off next Wednesday and will hopefully have updates soon after!
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