Chevy Bolt EV Forum banner

1 - 20 of 21 Posts

·
Registered
Joined
·
71 Posts
Discussion Starter #1
Noticed something today, while not moving and on flat road, foot "off" the brake and putting car in Park causes a horrible gear grinding noise. Replicated it twice. With foot on brake, no noise. So with brake on, is is disconnecting the transmission or something?
 

·
Registered
Joined
·
32 Posts
I hear this 'way too often because I park in an incline to be near my garage charger. If I am completely stopped then there is no grinding. I have always assumed it's the parking pawl being abused (by me).

Thanks for that link - now I'll try setting the parking brake first.
 

·
Registered
Joined
·
220 Posts
I have noticed some minor grinding if I am not completely stopped. I have learned to apply the break before engaging park.
 

·
Registered
Joined
·
71 Posts
Discussion Starter #9
i now always apply my foot on the brake, even though it "appears" i'm standing still. no more grindage
 

·
Registered
Joined
·
1,324 Posts
I come to a complete stop before applying the parking brake. I also prefer that the car is in park before getting out and while I'm at it, I recommend not only applying the parking brake after the vehicle has come to a complete stop but additionally, make sure the car is stopped before getting out if you are the driver.
 

·
Registered
Joined
·
1,106 Posts
I had this happen to me once, I was stopped on an incline (in a driveway) in L mode. When I put it in park I heard the evil grinding noise.

Ever since then I put the car in neutral with my foot on the brake, then engage the parking brake, then release the brake pedal and let the car settle against the parking brake BEFORE I put the car in park. This ensures there is absolutely no tension on the drive train when I engage park,
 

·
Registered
Joined
·
9 Posts
This happened to me twice in my first week of ownership. Once I made sure I was at an absolute stop before putting it in park, it hasn't happened again.
 

·
Registered
Joined
·
1,640 Posts
I had this happen to me once, I was stopped on an incline (in a driveway) in L mode. When I put it in park I heard the evil grinding noise.

Ever since then I put the car in neutral with my foot on the brake, then engage the parking brake, then release the brake pedal and let the car settle against the parking brake BEFORE I put the car in park. This ensures there is absolutely no tension on the drive train when I engage park,
Remember though that the noise (although it sounds like grinding gears) has nothing at all to do with the drivetrain, it's the low-speed automatic braking system being engaged.
 

·
Registered
Joined
·
210 Posts
Noticed something today, while not moving and on flat road, foot "off" the brake and putting car in Park causes a horrible gear grinding noise. Replicated it twice. With foot on brake, no noise. So with brake on, is is disconnecting the transmission or something?
OK everybody, what you're hearing is the parking pawl engaging, or trying to engage a little ratchet wheel. It's not a good noise, and it's not good for the car, so try to avoid it.


He calls it the parking linkage, and it engages the little cog wheel, with the square looking teeth, on the jack shaft.

27612


Imagine that spinning (much faster than the wheels) and jamming that little tooth in to it while it was moving. Angry.

There's nothing wrong with your car. Really make sure you're hard on the brakes for a second and completely stopped before you put it in P.

Every automatic transmission, and the chevy bolt, has one. https://www.google.com/search?q=parking+pawl
 

·
Registered
Joined
·
4,514 Posts
Ever since then I put the car in neutral with my foot on the brake, then engage the parking brake, then release the brake pedal and let the car settle against the parking brake BEFORE I put the car in park.
I do it the opposite way - at a full stop I pull up on the parking brake switch and then push the shifter forward into "N". You have to hold the shifter forward for a moment, and that's about the same length of time it takes for the parking brake to engage, so there's no extra waiting.

It's a little habit I've gotten into once the car comes to a full stop:
  • Pull up on parking brake switch
  • Push shifter forward and hold until it goes into "N"
  • Release the brake pedal
  • Push "P" on the shifter
  • Push the blue button to turn off the car.
 

·
Registered
Joined
·
210 Posts
NO!

Please actually read the posts in this thread, such as this one.
Snippy there.... Bold and all caps even. But you may yet be right.

I listened to those videos, and I heard the ABS sound, which makes perfect sense in that scenario. I personally still don't buy it in the parking scenario, and choose to believe the explanation that's been on the books for the last 80 years, but that's my personal opinion, which I'm sure you'll agree is worth a drop of piss.

But agree with me on this much - Stop your car before putting it in park.
 

·
Registered
Joined
·
1,640 Posts
Snippy there.... Bold and all caps even. But you may yet be right.

I listened to those videos, and I heard the ABS sound, which makes perfect sense in that scenario. I personally still don't buy it in the parking scenario, and choose to believe the explanation that's been on the books for the last 80 years
I'm snippy because every time we resolve these “oh noes, it makes a noise, it's the parking pawl” threads and finally get people convinced, some new person wanders in and starts a brand new one and the misinformation is shared yet again.

Over in another thread I noted that it's NOT the ABS system, is the “Low Speed Forward Automatic Braking System” that is activated to apply the brakes (in fairness I used to think the two systems were the same, but I was corrected about that, they're apparently distinct). I also linked to the videos that also got mentioned above where the brakes get applied and you hear the noise (you may need to crank up the volume to hear it on the video): inside the car and outside the car.

I also mentioned that in an even earlier thread is @dbostrom reports from his own experiment where he triggered the Low Speed Forward Automatic Braking System and found that it made the exact same noise. Also, earlier in that thread I explained why it could not possibly be the parking pawl.

It's not like we don't know these things. I've attached an image of the motor that includes the parking pawl. You can see that it is not directly on the motor output, but at an intermediate stage in the gearing.

The Bolt has a final drive ratio of 7.05:1, achieved by a ~3.5:1 gear connected to the wheels, connected to ~2:1 at the motor.

What that means, given the 80 inch outer circumference of the tires, is that moving the car forward one inch turns the wheels 4.5 degrees and parking pawl assembly through about 15.75 degrees.

Given the number of teeth on the parking pawl gear, a moment of the car of a few inches would cause about two or three clicks if it was slipping.

We don't hear two or three clicks.

Thus, your explanation is incorrect [...] it very clearly isn't the parking pawl.



but that's my personal opinion, which I'm sure you'll agree is worth a drop of piss
Let's agree that's it's worth no more than a drop of piss.
 

·
Registered
Joined
·
210 Posts
I'm snippy because every time we resolve these “oh noes, it makes a noise, it's the parking pawl” threads and finally get people convinced, some new person wanders in and starts a brand new one and the misinformation is shared yet again.

Over in another thread I noted that it's NOT the ABS system, is the “Low Speed Forward Automatic Braking System” that is activated to apply the brakes (in fairness I used to think the two systems were the same, but I was corrected about that, they're apparently distinct). I also linked to the videos that also got mentioned above where the brakes get applied and you hear the noise (you may need to crank up the volume to hear it on the video): inside the car and outside the car.

I also mentioned that in an even earlier thread is @dbostrom reports from his own experiment where he triggered the Low Speed Forward Automatic Braking System and found that it made the exact same noise. Also, earlier in that thread I explained why it could not possibly be the parking pawl.





Let's agree that's it's worth no more than a drop of piss.
Thanks for putting me in my place. I'm glad there's better men than me in this world to "correct" these impassioned, destructive and ignorant overtures to the vulnerable masses from the charlatans and mountebanks who subvert them.
 

·
Registered
Joined
·
10 Posts
Chevy Bolt Program Manager, please contact me, I just had my transmission replaced at 17k miles, I think it will happened again! By the way, I was the principal controls engineer on the Hybrid vehicle platform in Castleton, IN back in 1996. Look up the patent on this, US5751069A
I have for the most fixed the "operator error" of grinding the gears when going into park, it did occur once this week. I do highly recommend a simple software solution: Do not shift the gears if the brake pedal is not pressed AND make sure there is no motion detected on the drive motor for 1-2 seconds. The software needs to protect the vehicle.

Second, I get the same grinding gear noise when I open the door of the car! This occurs after a quick stop, power off the car and return within 5 minutes. I am baffled by this one. This has occurred one time this week.

The transmission was replaced because the "washer holding the spider gear in place was damaged" This in turn left metal debris in the fluid and resulted in a ground fault or error detection by the EV motor stator. The vehicle shut itself sown. Why did the filter and magnet not catch the debris...? GM please get back with me on a Failure Analysis report. I am very curious and would love to make the Bolt an even better car than it already is!
- Best Regards,
 
1 - 20 of 21 Posts
Top