High pitched noise from drive unit

[launchd]

Hi all,

I'm posting this here hoping you all may be able to shed some light on what this noise is. At the moment, our best guess is the front drive unit/a bad or faulty bearing design.

There is a large number of Tesla Model Y and 3 owners that have been vocalizing their concerns and frustrations with this noise. There is a very long thread over on Tesla Motors Club forums where you can read all about it. I don't know what the policy is for posting links to other forum boards, so I'll refrain from posting the link to it for now. The noise we are hearing, which can not be heard by everyone (frequency), is the noise heard (if you can hear it) in this video:

This noise is seemingly only present in cold weather (50 degrees fahrenheit or colder), above a certain speed (50mph). Although, some have heard it at lower speeds. It is even being heard on the new Model 3 Highland models.

Does anyone know what this noise is and/or how one might eliminate it? Tesla service centers have replaced front drive units over this noise, with some replacements solving the problem, but most failing to solve it. Tesla has taken a different stance on these drive unit swaps recently, and is now stating that although the noise is known to Tesla engineering, it is not something they are being authorized to perform a repair for.

[P.S.Mangelsdorf]

It sounds to me like its something rubbing. The way it cuts out over bumps makes me wonder if maybe there's either something rubbing against an axle or an issue in a CV joint. I'd take a look around the front suspension area and see if there's any witness marks.

The other alternative (i.e. not a mechanical issue) is that it is related to the switching frequency in the inverter, in which case there's really nothing to be done. I think that's less likely but its possible.

[launchd]

I do not believe it is suspension-related, unfortunately. Tesla SCs have been confirming that the noise we are all hearing is coming from the front drive unit. Those statements are being made (in multiple service orders, on multiple vehicles - Y and 3) after these SCs have had our vehicles for multiple days. No one (there are a lot of us) has been able to solve for this noise except for a very few edge cases (from awhile ago) where SCs were replacing the front drive units. Some of those replacements led to the noise being eliminated, some the noise becoming fainter and some, no change whatsoever. Now Tesla refuses to replace the front drive units. Frustrating noise to deal with - I wish I was lucky enough to not to hear it.

[P.S.Mangelsdorf]

Ok, follow up question - does the sound change pitch relative to speed? You note that most hear it above 50mph, but does it change as the speed varies?

[uhi22]

From the video linked above, took the audio, loaded it into Audacity (a really nice free audio processing tool), and see a quite stable tone at around 11kHz. Personally I cannot hear it, but it is clearly there. The frequency is stable, and the tone has some gaps. Would have been nice to see the speedometer at the video instead of the jeans

I'd propose to place some microphones into the interesting places to find out the loudest spot.

[Zieg]

That frequency seems to be almost the same as my tinnitus, had to really play with the volume to make sure I was hearing it.

If my car was doing that I would probably try to isolate it with an automotive stethoscope if possible. I'd be checking different parts of the drive unit as well as the wheel bearings, and anything metallic near the motor just in case it's being induced by the AC.

Sometimes manufacturers add mass to problematic parts, which will shift any harmonic frequencies up and hopefully out of the range of the human ear. The 2010 Chevrolet Camaro had terrible noise from its front brakes. For those models, the fix was to stick a bunch of lead wheel weights to the outside of the calipers. 2011+ models had a more professional-looking set of weights permanently affixed to the caliper. I wonder if something like that would help here? I feel like if I was being driven sufficiently insane by the noise and couldn't isolate it, I'd be sticking weights to various parts just to see if it helped.

[launchd]

Sorry about the video; it isn't mine; I snagged it from the 40-page thread about this issue on the other forum board. I added a few more sound clips below for reference.

Does the sound change pitch relative to speed?
It does not.

In November of 2022, a user on the other forum stated.
"I had mine resolved. They diagnosed it as a burnt out bearing in the front motor and they replaced the front drive unit."

As I mentioned earlier - some folks (very few) have had this noise solved by Tesla replacing their car's FDU. The cases of this that I've found were all in early 2023 or earlier. Now Tesla will not replace the FDU for this noise. A lot of us believe that this is a bearing issue (Tesla may have switched bearing suppliers or design at some point?), but we don't know how to prove it. I think it sounds oddly similar to the noise heard here... but I could be wrong.



"I recorded the sound and punched up the high frequencies to make it easier to hear."


"It's a high frequency noise that sounds sort of like crickets or hissing that appears when it's <70 degrees out, and you're driving >50 mph. Coming from the front drive unit. According to one service center, it's a bad bearing. You can hear the noise cut in and out at about 13s in the recording. It can come and go like that, even at speed."

[P.S.Mangelsdorf]

Given that it doesn't change frequency with speed, I am very skeptical that it is caused by any rotating components such as a bearing. In my opinion, that points to the inverter itself and likely its switching frequency. That could also explain Tesla's refusal to replace the units. Likely, they initially assumed it was a bearing issue like the LDUs had, but upon examination determined its an inverter noise issue.

[launchd]

Given that it doesn't change frequency with speed, I am very skeptical that it is caused by any rotating components such as a bearing. In my opinion, that points to the inverter itself and likely its switching frequency. That could also explain Tesla's refusal to replace the units. Likely, they initially assumed it was a bearing issue like the LDUs had, but upon examination determined its an inverter noise issue.

When the temperature gets warmer out, the noise completely goes away. Would this happen if it was the inverter/its switching frequency? The temperature being a variable is why we believe it may be bearing related. Colder temperatures impact lubricant viscosity, and metal will shrink or contract.

[Dadaaaaaaa]

Hi all,
Furthermore, the noise completely vanishes after a supercharge.
And it’s audible only during cruising (when the FDU is idle).

[P.S.Mangelsdorf]

the noise completely vanishes after a supercharge.

Does it come back as SOC decreases, or does it only come back after a Level 1/2 charge?

And it’s audible only during cruising (when the FDU is idle).

That's interesting.

Does everyone who has this issue agree that it is coming from the front of the car? Is anyone hearing it coming from the rear and/or back seat area?

[launchd]

Yes, I would say that at this point, we all agree that it is coming from the front of the vehicle, not the rear.

Here is the thread on the other forum is you want to read through all forty pages.

[Dadaaaaaaa]

Does it come back as SOC decreases, or does it only come back after a Level 1/2 charge?

No, the noise only reappears when the car cools down after being parked for a while. During long trips, the noise does’t return between supercharges.

[P.S.Mangelsdorf]

No, the noise only reappears when the car cools down after being parked for a while. During long trips, the noise does’t return between supercharges.

That, combined with the frequency not varying with speed, indicates to me that this is not coming from the drive unit. It's coming from some other system, likely cooling. Could be a pump, could be a valve, could be a fan. I'd lean towards valve.