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Discussion Starter · #1 ·
Hi everyone,

My 2017 Bolt has developed a clack/crunch sound that occurs when the driveline is loaded/unloaded indicating play somewhere. It is most evident when driving in stop-and-go traffic in L. My car is pretty high mileage at over 200,000 kms. I have owned it since 192,000 kms.

I took the car to the dealer this week. They reported after a test drive that the noise is coming from the final drive of the transmission. The "transmission" is more than a transmission in our cars: it is the motor, fixed gear reduction, and differential all-in-one. The quoted cost to replace this part: over $8500 CAD. The part alone is over $5100 CAD.

I have read on this forum of others experiencing this issue (under warranty, thankfully for them): Creaking/Clunking at Low Speed

For a video I shot of the sound, see
. In the latter part the video the sound is more obvious because I stopped talking over it. Turn up the volume while watching.

If anyone has any leads on a used drive unit, ideally in Canada, I'd appreciate it.

I plan to change the fluid in the transmission/drive unit shortly, mostly to inspect for metal.

If you want to learn more about the transmission/drive unit, see
for a great tear-down video.

Andrew

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Could you find a transmission shop that could overhaul the transmission and just replace damaged or worn out parts instead of replacing the whole transmission?
For example, I rebuilt the 5 speed manual transmission in my 1 ton Dodge pickup with new bearings, thrust washers, seals, etc. for $185 in parts. The Bolt assembly looks much simpler to me.
 

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OK so in my old Mazda 6 I was getting that kind of noise when the motor mount bushings went bad and the mounts were just banging metal on metal. I'm not saying the service center is wrong but, maybe get a second opinion?
That's what about 124,000 miles?
 

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This might be relevant to you. You can see the videos where the play was between the inner CV and the axle stubshaft / transmission and how it clunks on accel / decel.
 

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Discussion Starter · #5 ·
Could you find a transmission shop that could overhaul the transmission and just replace damaged or worn out parts instead of replacing the whole transmission?
For example, I rebuilt the 5 speed manual transmission in my 1 ton Dodge pickup with new bearings, thrust washers, seals, etc. for $185 in parts. The Bolt assembly looks much simpler to me.
One trouble will be finding parts: Chevy only seems to sell the gaskets and filter from the parts websites I browsed. Another problem is that the unit requires special tooling to disassemble because of the very strong magnets on the rotor.

You’re right that the transmission is much simpler than a shifting manual or auto.

Andrew
 

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Discussion Starter · #6 ·
OK so in my old Mazda 6 I was getting that kind of noise when the motor mount bushings went bad and the mounts were just banging metal on metal. I'm not saying the service center is wrong but, maybe get a second opinion?
That's what about 124,000 miles?
Thanks. I asked that the shop specifically check CV joints, hubs, and motor mounts when I brought it in. I plan to pull the belly pan and change the fluid myself, so Ill have a look when I’m under the car.

Andrew
 

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Discussion Starter · #7 · (Edited)
This might be relevant to you. You can see the videos where the play was between the inner CV and the axle stubshaft / transmission and how it clunks on accel / decel.
Thanks. Ill check that out.

Andrew

Edit: Checked out the linked video. It is a totally different sound from what I am experiencing.
 

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Have you jacked up the car and rotated the front wheel to see if you can feel the play? I'm wondering if this might be in the CV joints, as it seems to me that they're more likely to be an issue before the transmission is. If you jack the car up and move the wheel you might be able to see if there's any play in the inner or outer joint on each side.

I'd also consider going to an independent shop to get their opinion, certainly before spending that kind of money on a repair. If it is something like a CV joint they'd be able to diagnose and repair it even though the Bolt is an EV.

Edit - I see that ZBrown has already suggested this, I concur.
 

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Thanks. Ill check that out.

Andrew

Edit: Checked out the linked video. It is a totally different sound from what I am experiencing.
I was more referring to the clunking sound in the first minute of the video in post #19 of that thread.
 

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I have this exact same issue, I started noticing it back in August. It only happens if the weather is warm, over 60F.

Here is my video:

Happens several times after the 30 second mark. I also have a clunking sound when going over uneven pavement.
 

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Mountabolt, Yours sounds more like a rubby squish sound... sorry that is how I hear it. Maybe more of a tie rod kinda thing, CV Joint.

adoepner Yes it is the Transmission. It took 2 dealers to actually LISTEN to me and when they changed it all was good. FYI, there is another thing that it could be.. Link something and...... shoot I can't think of it... Sway Bar, in the front end also makes a sound like that. IF the sway bar, you will see a wear mark on the metal up inside.
You will have to google a video on how/where to look for the wear marks as I can't remember.
 

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I took the car to the dealer this week. They reported after a test drive that the noise is coming from the final drive of the transmission. The "transmission" is more than a transmission in our cars: it is the motor, fixed gear reduction, and differential all-in-one. The quoted cost to replace this part: over $8500 CAD. The part alone is over $5100 CAD.
Before paying that price you could look into a buyback to see if you get a decent offer. Although that takes 4+ months for most so it depends on if your car will continue as is or get worse and fail completely. Perhaps you could go the rental car route too while waiting.
 

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Discussion Starter · #13 ·
A post on a Bolt facebook group by Dmitri Kozhevko put me onto a possible cause for this issue unrelated to the transmission. See https://www.drive2.ru/l/479851339568906549/ (for Chevy Cruze, but Bolt is basically the same). I ordered 2x GM #11611964 Axle Assembly washer and replaced them myself. On disassembly, I found that the right washer was cracked and deformed.

Replacing the cracked washer solved the issue. No more noise!

Hope this helps others ... and maybe GM will put out a service bulletin and stop recommending unnecessary transmission replacements!

Andrew
 
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