Help! California Whining Sound From Rear

Sorry to see you're having a problem with your car. You didn't say if the noise came from the front or the back. Does the noise come from the front, back, one side of the car or directly below (centre of the car)? Is the noise louder inside the car or outside (open window)?

Your comments are focused on the rear so... usually noise from the rear are due to worn hub bearings (one side or the other) or fuel pump. It could also be differential but I've never had a differential issue with any car so no first hand experience with that but whining noises would be consistent with any worn gear. Internal wear in the DCT should be picked up by heat sensors because any wear would result in elevated operating temperatures and the ECU managing the DCT is very touchy about heat. I don't know of any other mechanical components back there that would make a whining noise related to engine or vehicle dynamics.

As regards New Power Warranty coverage, if you haven't already reported this problem to the dealer, you should not delay. Warranty coverage is also based on mileage and not just time when the problem first appear. I believe NPW expires after 90,000 km.

My copy of the NWP states...

"...Parts covered by the New Power extended warranty in detail:
...

• Mechanical gearbox/F1 gearbox: gearbox casing and differential housings, including all internal components.
• F1 Power Unit: electric pump, valves; actuator, ECU, selected and engaged gear sensor (oil seals and oil leaks in general not covered).
• DCT gearbox: gearbox and all internal components, ECU (oil seals and oil leaks in general not covered).
...
• Fuel and induction system: injectors, throttle bodies, air flow sensor, intake manifold, pressure regulator, temperature sensors, fuel pipes, fuel pumps.​

..."​

 

A good way to listen for noises is to drive down a NARROW street with a building on one side and open area on the other.

The building side will reflect and magnify the noise, the open area will dissipate the noise. You drive down the street in one direction and then go back in the opposite direction, preferably driving down smack in the middle of the street when there is no other traffic - very early morning on the weekend being the best time to do this. If the noise is louder in one direction then the noise is from the building side of the car.

You can also ask a friend to stand on the building side of the street and to listen for the noise. The car is quieter when you are in a high gear so the whining will be more easy to make out. As you already pointed out the noise is faint and the car is noisy in low gears.

The most common whining noise from the rear of a car is due to worn hub bearings and it usually only affects one side at a time. The noise will get worse over time as the bearings degrade further. 18k miles is not enough mileage to cause bearing wear but if you tend to drive a lot on rough roads and have 20" or even bigger wheels, the bearings can get damaged, especially if the car has smacked a curb before.

 

I also have a ‘10 California & notice this faint sound. The dealer took it out during my last service & said that a slight hum from the transmission was normal (you are sitting right on top of it in the California). They renewed my Power Warranty, so I guess I’m covered in case it turns into something major.


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Actually, mine is most noticeable as I'm taking off in lower gears. Very faint noise, however...

 

It may also be helpful to describe the quality of the noise, whether it's lower frequency, mid or high frequency.

With speed-sensitive noises made by spinning mechanical components, when the car is in low gears the driveline is more prone to amplify and project noise caused by any mechanical imbalance, because the frequency of the sound is lower and easier to notice. Each car also has its own resonant frequency at which point noises are even amplified. At any rate, driveline noises at very low frequencies, would actually sound like rattling. As the noise frequency increases, it becomes a whine, and then a buzz, a hiss and then most people won't hear it any more if it exceeds 15kHz although I would doubt if anything is vibrating at that high a frequency on your car.

 

Curious what they do in that case... Obviously with you being in the UK it's not that Italy is very far, but it's not across the road either. How long are you without the car? Or are they swapping in another gearbox so you aren't without your car for God knows how long while some techs in Italy tear apart the gearbox to see if there is more to the issue?

 

Well, it's good to see your dealer has initiated a repair attempt but I'm surprised they had to ship the gearbox to Italy. My dealer can service DCTs themself and are quite used to servicing them on their Challenge race cars. Perhaps the factory wants to look at the problem firsthand. At any rate, since 6th (EVEN) and 7th (ODD) gears are located on separate input shafts in the 7DCL750, I think it's more likely a problem in the differential. I hope they got you a cabrio C class.

 

...it could also be the bearings that separate the 2 input shafts as they would be spinning regardless of which gear the gearbox is in.

Hopefully, the factory will provide you a full explanation once they sort this out.

 

I've also received very good service from Ferrari factory customer service (Italy). Someone emailed me and told me to contact her if I needed anything. Luckily I didn't have to take her up on her offer but it was very reassuring to receive direct support from the factory. Hopefully, they will sort out your issues quickly.

Assuming you also have a factory contact, I would check with that person to follow the service of your car's gearbox, from confirming receipt of the item to being briefed on the process and keeping tabs on the specific milestones in that process. That way, you will have a better idea of just what they plan to do and when they will complete their work.

As for the C-Klasse saloon, it's OK if you just need a decent car to drive to work but if you're missing the convertible roof you might want to request a change to a cabrio - I think it's a fair request.

Good luck and keep us abreast.