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Discussion Starter #1
Hi all, I've had my 2014 Volt for a little over 4 years now, love it. I started driving almost exclusively in L about 3 years ago. Last month I noticed a slight "knock" noise when I would press or release the Go pedal. Not anything super loud but enough that even my girlfriend noticed it. It doesn't happen when driving in D or in Reverse so I am assuming it has something to do with the aggressive regen mode when driving in L.

Does that make sense?

I intend to bring it in to the dealer to have it checked but it's not always easy to get them on board with these kind of odd little issues.

Thanks
 

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The knock that you are experiencing may be a loosening of (or wear) in the drive train that is exacerbated by the aggressive (shock) regen occurring when initiating L. I noticed the beginnings of that early on and decided not to use L again. I modulate my speed with the brake pedal. I believe that llninja opened my eyes to the fact that the brake pedal allowed infinite adjustment of regen (and friction braking when needed) whereas L imposed a fixed imposition of regen (with a shock to the drive train). After some years of using the brake pedal for regen, I realize that this mode is far better than shifting into L. I recommend that you learn to use the brake pedal in lieu of L to slow down.

There are times when L is desired. I have found that driving on mountain roads with frequent curves (US 1 in California is one example) is beneficial for controlling speed. Also, when in stop and go traffic with frequent speed-ups and slow-downs, L is beneficial. Driving with cruise control down mountain roads with L engaged prevents any speed increase.
 

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If it is just one "knock" as you call it each time you press or let off the go pedal, my guess would be the axle nuts. If you have been on this forum for very long, you should have seen something about this very common problem. I had it on my 2011, free and easy to try. If you can get the center cap off and have the right size socket (I don't remember the size) you can tighten without jacking up the car.
 

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The original axle nuts take a 32MM deep socket.
 

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Yes, and there is an upgraded larger nut available at the dealer. 36mm.
 

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Thinking about it, I would go with post #2 in that it could be the lash in the drivetrain being amplified by driving in L. I can feel it in the drivetrain of my '14.
 

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Discussion Starter #7
I will double check the axle nut but I would think that would happen regardless of whether I was driving in L or not.

Sounds more likely to be what JBJ described in #2. Even if I do modify my driving technique I'd probably want to get that fixed first. I'll set up a dealer visit and share this info with them.

Thanks!
 

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Yes, it would happen if you were driving in low or not, I have had it happen while driving in low and drive.
I originally drove the car in low, had the issue, dealer fixed it and I started driving in "D". The dealer had changed the nut on the driver's side and torqued to spec.

About 6 months after the dealer fixed it and after I had been driving in "D" during that time, it started happening again. As the dealer wasn't willing to take it apart to change the washer behind the hub and bearing as many suggested here I chose to do the repair myself. I pulled everything apart on both sides, changed the washer, installed a new nut and torqued to spec. Haven't had a problem since and I am now back to driving in low.

If driving in "D" when there is slop in the joint, when you initially apply the brake, regen is enabled and you'll hear another click as the movement in the hub and output shaft interface begins moving in the opposite direction. The click, click sound of the backlash that causes the noise is easier to replicate in low but it still happens in drive.

Many forget that when in "D" and you apply the brake you invoke regen to slow the car. The end result is the same as driving in low. If you push the brake to slow the car faster than regen will, the friction brakes will assist in coming to a rapid and complete stop.

Really little difference if you use "L" or "D" to propel the car forward.
 

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Discussion Starter #9
I will try it again in Drive and pay more attention to the pressure I am using to see if I can replicate it there. Thanks
 

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Hi all, I've had my 2014 Volt for a little over 4 years now, love it. I started driving almost exclusively in L about 3 years ago. Last month I noticed a slight "knock" noise when I would press or release the Go pedal. Not anything super loud but enough that even my girlfriend noticed it. It doesn't happen when driving in D or in Reverse so I am assuming it has something to do with the aggressive regen mode when driving in L.

Does that make sense?

I intend to bring it in to the dealer to have it checked but it's not always easy to get them on board with these kind of odd little issues.

Thanks
 

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I had a similar problem but w/o the "knock" noise. When I accelerated, the car would seem to hesitate for a very brief moment and then lurch forward. The same happened when I would take my foot off the accelerator. I took it to the dealer and they diagnosed and fixed loose engine mount bolts. That did fix it. Unfortunately that was NOT covered by my extended warranty :-(
 

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The knock that you are experiencing may be a loosening of (or wear) in the drive train that is exacerbated by the aggressive (shock) regen occurring when initiating L. I noticed the beginnings of that early on and decided not to use L again. I modulate my speed with the brake pedal. I believe that llninja opened my eyes to the fact that the brake pedal allowed infinite adjustment of regen (and friction braking when needed) whereas L imposed a fixed imposition of regen (with a shock to the drive train). After some years of using the brake pedal for regen, I realize that this mode is far better than shifting into L. I recommend that you learn to use the brake pedal in lieu of L to slow down.

There are times when L is desired. I have found that driving on mountain roads with frequent curves (US 1 in California is one example) is beneficial for controlling speed. Also, when in stop and go traffic with frequent speed-ups and slow-downs, L is beneficial. Driving with cruise control down mountain roads with L engaged prevents any speed increase.
I've owned my 2014 for about 3 years. It now has 90K on it. I've wondered about braking vs L for regen. I have a 38 mile commute in the WNC mountains. I had to replace the rear brakes about 3 months after I bought the car as the passenger side had zero pad left (Brakes- Checked on the dealers survey. I have to wonder what their criteria was.) so I hesitate to use the brakes a lot. The "big mountain I cross is almost four miles up/down each way.

I have from time to time also made my commute in L but never noticed a knocking sound. My impression though it that L recovers more battery than braking does. Is there any science on this either way? On my four mile climb I use about 16 miles of battery and only recover 4-5. I'd try brakes only if I could get my dad's voice out of my head ("Stop using the brakes! Use low gear!").
Thanks
 

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If it is just one "knock" as you call it each time you press or let off the go pedal, my guess would be the axle nuts. If you have been on this forum for very long, you should have seen something about this very common problem. I had it on my 2011, free and easy to try. If you can get the center cap off and have the right size socket (I don't remember the size) you can tighten without jacking up the car.
I've had this with my Gen 1 and my 2004 Impala. It's a known maintenance issue with the particular drive train. Either tighten them down once a year or so, or use the recommended replacement nut and washer from GM. Both work just as well.
 

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Discussion Starter #14
I've been experimenting a bit more and it does happen in D, just not as obvious, I really have to listen for it there. I will check the axle nuts. Thanks!
 

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I've owned my 2014 for about 3 years. It now has 90K on it. I've wondered about braking vs L for regen. I have a 38 mile commute in the WNC mountains. I had to replace the rear brakes about 3 months after I bought the car as the passenger side had zero pad left (Brakes- Checked on the dealers survey. I have to wonder what their criteria was.) so I hesitate to use the brakes a lot. The "big mountain I cross is almost four miles up/down each way.

I have from time to time also made my commute in L but never noticed a knocking sound. My impression though it that L recovers more battery than braking does. Is there any science on this either way? On my four mile climb I use about 16 miles of battery and only recover 4-5. I'd try brakes only if I could get my dad's voice out of my head ("Stop using the brakes! Use low gear!").
Thanks
The thought that friction brakes are applied sooner than when braking in L is incorrect. Think of what is desired: slowing down. To accomplish that, regen is first imposed, either with the application of the brake pedal or with the fixed amount called for with L. Increased application of the brake pedal to further slow down, or just to maintain the current rate of deceleration, will call for increased regen to a maximum beyond which the friction brakes begin to be applied. The application of friction brakes does not occur sooner with the sole use of the brake pedal. As far as when the friction brakes are applied, it doesn’t matter whether or not you use L. One of the nicer things about using the brake pedal exclusively is how smoothly you can decelerate. Of course, in driving on some of the back roads it may be desirable to have the immediate increased slow-down that you get in L when you let off the go pedal. I hope that I could make that clear.

I often visited my aunt and uncle in Burnsville as a youth and again visited the area last November and stayed in Spruce Pine for the night. The temperature dropped to nine degrees over night. My Volt started right up the next morning at 5 AM. That experience not withstanding, I envy you your chance to enjoy the beauty of the area every day.
 
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