[grommet]

So one of the downsides of owning two Bolts (2017 and a brand-new 2019) is that it offers up the opportunity to compare every idiosyncrasy between the two cars. The 2017 LT has been rock solid...no complaints there. The 2019 Premier, however, definitely has a “noisier” traction motor, especially when regen braking in “L” at certain speeds. My concern of course is that I have a less-than-perfect traction motor which is nothing you want to see with a brand-new car.

What am I hearing?

There appears to be a secondary noise that becomes audibly louder when applying moderate regen braking around 23MPG. I can only describe it as a soft warble or resonance that I can trigger around that speed (again, with moderate regen braking at that speed). It’s definitely NOT there in my 2017, like not at all. Moreover, the traction motor all around just sounds noisier than my 2017.

I suspect that there are no real differences b/w the 2017 and 2019 w.r.t. the drive train so the noise I’m hearing is a defect and shouldn’t be there. I recognize that this could be a minor issue with no impact on the longevity of the traction motor or related components...but it equally could be cause for concern.

I suppose I’ll take it into the dealership and have them look at it. Not sure what I’m asking of this forum other than perhaps insight into what it could be. I’d like to go in armed with helpful information as I suspect they’ll have no clue what’s going on.

 

[121 Kw]

Ask to have them drain the transmission fluid into a clean pan and look for metal. Maybe even go so far as to ask for a sample of the drained oil to send out for metal testing to see if the gear set or bearing is wearing. Commercial vehicles often have their fluids sampled and sent to a lab for a metals check to try and catch problems before they become catastrophic failures.

 

[grommet]

Ask to have them drain the transmission fluid into a clean pan and look for metal. Maybe even go so far as to ask for a sample of the drained oil to send out for metal testing to see if the gear set or bearing is wearing. Commercial vehicles often have their fluids sampled and sent to a lab for a metals check to try and catch problems before they become catastrophic failures.

That's a great idea. In your experience, how urgent is it to take it in for service if there is premature gear or bearing wear? The car only has 500 miles and I prefer to drive it a few more miles to ensure there isn't a false negative if that indeed is the problem.

P.S. I found the relevant service manual section that might deal with this (attached). It also references the front differential although I doubt that's the issue.

 

[121 Kw]

I don't have any long term experience with the Bolt, mine only has ~1,200 miles, but equating a manual transmission or rear end gear, it's unlikely to go away.

As for panning out to catastrophic failure, a ball bearing or gear noise in either of the above applications could go tens and tens of thousands of miles without every crossing into catastrophic failure, just noisy. Especially at the Bolt's HP/TQ/weight level.

My "feeling" is the gear set has a defect that causes whine on decel. May not even put metal into the oil, just how the gears mesh cause it to sing. Will never lead to failure, but GM regularly warranties noisy rear axles for simply being noisy.

 

[chartquist]

There appears to be a secondary noise that becomes audibly louder when applying moderate regen braking around 23MPG. I can only describe it as a soft warble or resonance that I can trigger around that speed (again, with moderate regen braking at that speed). It’s definitely NOT there in my 2017, like not at all. Moreover, the traction motor all around just sounds noisier than my 2017.

Hmmmm, are you sure that you're not referring to the pedestrian warning sound that the car emits? Sounds like maybe it's been disabled in your 2017 but is operational in your 2019. I believe +/- 20mph is when the sound is triggered. One quick way to tell whether it's the noisemaker is when shifting in and out of park (no noise in park, and noise generator when in gear).

 

[grommet]

Hmmmm, are you sure that you're not referring to the pedestrian warning sound that the car emits? Sounds like maybe it's been disabled in your 2017 but is operational in your 2019. I believe +/- 20mph is when the sound is triggered. One quick way to tell whether it's the noisemaker is when shifting in and out of park (no noise in park, and noise generator when in gear).

It's disabled in my 2019 too.

 

[chartquist]

It's disabled in my 2019 too.

Sooooooo much nicer.

 

[121 Kw]

[hi-jack]

How are you disabling it?

[/hi-jack]

 

[grommet]

[hi-jack]

How are you disabling it?

[/hi-jack]

Pull the 7.5a fuse labeled “PFAF” as indicated on the back side of your fuse cover. I believe it’s fuse 34.

Now there may be legal implications for doing this, so do it at your own risk! <—IANAL

 

[SodePop]

I believe my 2019 bolt does this too. However, the sound I hear is more like a static/whooshing sound. It happens at lower speeds during regen braking, but also when I am accelerating as well, but only briefly. I thought it was the speakers originally, but it's definitely the motor. I can also clearly hear it with the windows up. And it's audibly the same when they're down as well. I might take it in, but they are probably going to say that's normal. Maybe so. But if earlier models don't do it, then it possibly could be an issue.

 

[neutrondrip]

I notice something similar in my 2017 but only when the A/C compressor is on and working hard. I also notice the same thing when burning a lot of kWs accelerating with the A/C working hard.

I attributed it to the A/C interacting with either the power or coolant flow when it's on full blast.

 

[BlueStreak]

So one of the downsides of owning two Bolts (2017 and a brand-new 2019) is that it offers up the opportunity to compare every idiosyncrasy between the two cars. The 2017 LT has been rock solid...no complaints there. The 2019 Premier, however, definitely has a “noisier” traction motor, especially when regen braking in “L” at certain speeds. My concern of course is that I have a less-than-perfect traction motor which is nothing you want to see with a brand-new car. .

Our 2017 is noisier in hot weather regen than our 2019. Also, the seat of my pants feels like the 2017 regen brakes better than the 2019's. In hot weather regen in the 2017, I can actually feel a very subtle high frequency vibration in the drivers floorboard.

Still love both though, now 21k on the 17, 4k on the 19.

 

[MDBolt]

I notice something similar in my 2017 but only when the A/C compressor is on and working hard. I also notice the same thing when burning a lot of kWs accelerating with the A/C working hard.

I attributed it to the A/C interacting with either the power or coolant flow when it's on full blast.

Yes!!! I get the same issue in 90+ degree weather (which unfortunately we’ve been getting a lot of recently here in MD) with the A/C slaving away to get it down to 70. As soon as the A/C settles down the whooshing goes away.

 

[grommet]

Yes!!! I get the same issue in 90+ degree weather (which unfortunately we’ve been getting a lot of recently here in MD) with the A/C slaving away to get it down to 70. As soon as the A/C settles down the whooshing goes away.

You're probably hearing the A/C compressor itself...you can hear it spool up on a warm day after charging since it's also used to condition the battery.

My sound is definitely something with the drivetrain as the tone tracks perfectly with the speed of the car. There are two sounds when accelerating/decelerating...a high pitched followed by a lower pitched tone. Both appear to be normal...the problem I have is the lower pitched tone is audibly louder and also resonates around 22 MPH. I'm having the dealer analyze the transmission fluid once I hit about 1000 miles to see if there's any premature wear.

 

[MDBolt]

The noise I’m hearing is distinct from the compressor and battery conditioning noises. It’s like the regen is amplified, with a much distinct whoosh to it compared to normal usual operation, and like the other poster above, it appears to be more prominent during abnormally hot days when the AC is working extra hard. I’m wondering if there’s something there as was suggested.

 

[neutrondrip]

The noise I’m hearing is distinct from the compressor and battery conditioning noises. It’s like the regen is amplified, with a much distinct whoosh to it compared to normal usual operation, and like the other poster above, it appears to be more prominent during abnormally hot days when the AC is working extra hard. I’m wondering if there’s something there as was suggested.

Yeah, sounds to me to be pretty similar to what you're describing, and only during regen or heavy acceleration. It's a whoosh / vibrating sound with slight vibrations I can feel through the accelerator pedal and floorboard.

 

[MikeyBolt]

My 2019 makes a similar sound when driving in L and coming to a stop with regen. I've not been worried about it. My 2017 Volt made a lot more (and a lot stranger) sounds when driving. It's not very loud and sounds like a typical motor wind-down sound. I'd almost equate mine with a similar sound to a slight differential gear whine which is probably normal given the transmission and gears are in the front.

Mike

 

[Torhnton]

what the... that was weird. Reboot, and if it still sounds like that, get it checked out.

 

[SodePop]

what the... that was weird. Reboot, and if it still sounds like that, get it checked out.

Reboot? What exactly are you referring to? Sorry, I don't get what you're talking about.