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Hi, my "new" 2014 Volt developed a peculiar, faint thumping or rumbling (not a 'clicking') noise from the front end when deaccelerating in L or if braking in D. The car has 44,000 miles on it. The sound was most prominent if slowing while turning right, like into a parking lot, etc.

The dealer said they found excess play in the inner left axle where it exits the transaxle. They said they tried tightening the axle nut(?) but that didn't fix the noise. They escalated it to GM and the engineers consulted with them. They eventually diagnosed the axle itself was worn and needed replacement. GM told the dealer they are seeing more of these inner axle failures on Volts because heavy driving in L puts additional stress and wear on the left axle (tripod joint?) during heavy regeneration, specifically. (i.e. the part may not have been designed robustly enough to accommodate it).

The dealer wanted over $750 to replace the axle, until I gently reminded him it was under warranty....

Has anyone else had this problem?

How much does an OEM brake job cost for a Volt?
 

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Something odd going on here. The decelerating forces in L should be less than accelerating forces in normal driving, The forces in brake pad braking would be greater than regen. Then there is extreme forces like accelerating on slippery pavement, hitting pot-holes and accidents. Looks to me like regen would be the most gentle of forces. Probably a factory defect or some accident.
As far as the brakes: They would probably be twice the cost of a normal brake job since the rotors are specially treated to not rust and cost about double a cheap rotor. Brake job about $200 a wheel. Now why do you need a brake job at 44k miles? My 2015 shows almost no brake wear at 55k miles. I drive in L.
 

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Discussion Starter #3
Something odd going on here. The decelerating forces in L should be less than accelerating forces in normal driving, The forces in brake pad braking would be greater than regen. Then there is extreme forces like accelerating on slippery pavement, hitting pot-holes and accidents. Looks to me like regen would be the most gentle of forces. Probably a factory defect or some accident.
As far as the brakes: They would probably be twice the cost of a normal brake job since the rotors are specially treated to not rust and cost about double a cheap rotor. Brake job about $200 a wheel. Now why do you need a brake job at 44k miles? My 2015 shows almost no brake wear at 55k miles. I drive in L.

I dunno. I'm not an engineer but I would imagine that the torsion forces (?) trying to stop a large circumference drive wheel with very large loads on it, by placing a braking force at the opposite end of the axle, upon the much smaller end of the axle itself, has got to put vastly multiplied forces onto and through the CV joint? Otherwise, in an ICE, those forces would have been absorbed mostly by the brakes, which are securely bolted to the structure, and the friction pads and calipers absorb the forces. (The rest partially absorbed by the transmission.) In an ICE the axles have to deal with the force of starting the vehicle from a stop, but in EV/PHEVS with high regen they have to deal with both starting and stopping forces.

No, thankfully I don't need a brake job thankfully! I'm just trying to figure future costs of brakes vs possible new axles.

The dealer wants to charge me almost $800 for a 5-year fluid change to all 3 cooling systems, but that's another topic.
 

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Well, this thread has me concerned. I've had my 2014 Volt for 5 years, has 35K miles, and I drive exclusively in L. The only car trouble I've had was the 12V battery died a couple years ago while I was away on vacation. I've had the oil changed once. The original brake pads have started to squeal at very low speeds while cold, so I figured I'd need to get the pads replaced at the next maintenance visit. $200 a wheel? How is that possible? Is that including replacing the rotor? I'd better get the pads replaced before the rotors gets damaged.
 

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Thanks for sharing this post and for including the comments from GM.

I wonder if this is also a concern with the Gen2 and the 'Regen on Demand' paddle. Should we infer from this GM diagnosis that use of the regen paddle eventually leads to excessive axle wear? I'm making the assuming here that the regen is achieved the same way whether the paddle is pressed or if the car is in L.



Hi, my "new" 2014 Volt developed a peculiar, faint thumping or rumbling (not a 'clicking') noise from the front end when deaccelerating in L or if braking in D. The car has 44,000 miles on it. The sound was most prominent if slowing while turning right, like into a parking lot, etc.

The dealer said they found excess play in the inner left axle where it exits the transaxle. They said they tried tightening the axle nut(?) but that didn't fix the noise. They escalated it to GM and the engineers consulted with them. They eventually diagnosed the axle itself was worn and needed replacement. GM told the dealer they are seeing more of these inner axle failures on Volts because heavy driving in L puts additional stress and wear on the left axle (tripod joint?) during heavy regeneration, specifically. (i.e. the part may not have been designed robustly enough to accommodate it).

The dealer wanted over $750 to replace the axle, until I gently reminded him it was under warranty....

Has anyone else had this problem?

How much does an OEM brake job cost for a Volt?
 

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Discussion Starter #6
Thanks for sharing this post and for including the comments from GM.

I wonder if this is also a concern with the Gen2 and the 'Regen on Demand' paddle. Should we infer from this GM diagnosis that use of the regen paddle eventually leads to excessive axle wear? I'm making the assuming here that the regen is achieved the same way whether the paddle is pressed or if the car is in L.
I don't know how to post photos here but my receipt states they "called TAC #9-4986233600 and also advised to replace left front axle shaft 3040220 .9" The part numbers were 22816826 axle shaft, 11547142 washer, and 11611687, nut. $597 warranty cost.

Maybe the Gen 2 with the paddle shifters changed the designs?
 

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Maybe, I'm sure someone out there knows. On the Gen2, there's nothing I can find in the manual that warns against using Regen on Demand excessively or above/below a certain speed, etc. It also recommends using Low in "heavy stop-and-go traffic" and when traveling downhill. BTW, I believe TAC stands for Technical Assistance Center. Not sure what the numbers designate.

I don't know how to post photos here but my receipt states they "called TAC #9-4986233600 and also advised to replace left front axle shaft 3040220 .9" The part numbers were 22816826 axle shaft, 11547142 washer, and 11611687, nut. $597 warranty cost.

Maybe the Gen 2 with the paddle shifters changed the designs?
 

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I can't imagine how (much less why) an axel could be engineered such that torsion in one direction is okay, but torsion in the other direction is would cause exceptional wear. Not fracture, not stress cracks, wear. It's even still turning in the same direction.
 

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The outer CV/axle to hub nut and spline back-lash would be a one time click. Once on regen deceleration or reversing, once on forward acceleration, but not repeated, not "thumping" nor "rumbling". Tightening the outer axle to hub nut could (as I did to both of my axles) correct a one time click at the change from decel to accel, but won't do jack for a rumble. Noise from the front end? Tighten the nuts. When all you have is a hammer, everything looks like a nail.

Here's where the big problems with the use of "L" mode as a cause of inner joint failure are:

Regen is limited to some maximum deceleration rate, some maximum number of kW. That limit is LESS than the 100+ kW of acceleration. You simply can not apply more regen braking torque into the axle than the forward torque of acceleration applies.
Any braking force needed above this is applied by the hydraulic friction brakes located at the outer end of the axle on the Volt. Some cars have inboard brakes and these do apply braking force through the axle to the wheel/tire, but not the Volt.
Use of L rather than D does not increase the limit of that regen. It only applies harder at any given point, but does not exceed that factory set limit. The foot brake pedal, in D, can apply regen from zero kW to the max limit. The use of L causes that to be, I dunno, 20 kW(?) up to the same max limit. In either drive mode the max braking load that can be applied through the axle is less than the 100+ kW maximum forward drive load.

The inner joint may well be worn, but it isn't due to regen braking.
Inner joints, and outer joints, too, will wear. They wear based on their direction of frequent use. The contact surfaces used in forward movement have more use than the contact surfaces used in reverse (or regen). Eventually this leads to rumbling as the amount of play between the forward and reverse contact surfaces increases as those surfaces erode. SAAB used to (mid-60's) suggest in their factory service manuals to swap the complete (equal length) left and right axles side for side to extend intervals between replacements. Although this only moved the worn and 'noisy' forward drive surface of the joints to the reverse side, the opportunities of detecting "rumbling" at 30 mph in reverse are much less.

If the inner joint boot was damaged (cut, split, chemically softened, pinched during install or service) allowing grease contamination, or if there were insufficient grease as assembled, that I'd believe could lead to an earlier than expected joint failure, but 45k mile failure, on an inner joint, is NOT caused by use of "L".
 

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Well, this thread has me concerned. I've had my 2014 Volt for 5 years, has 35K miles, and I drive exclusively in L. The only car trouble I've had was the 12V battery died a couple years ago while I was away on vacation. I've had the oil changed once. The original brake pads have started to squeal at very low speeds while cold, so I figured I'd need to get the pads replaced at the next maintenance visit. $200 a wheel? How is that possible? Is that including replacing the rotor? I'd better get the pads replaced before the rotors gets damaged.
My 2011 has 97k miles, original pads, no squealing. Do you hit the brakes hard a lot?

Yes, when the wear indicator starts making noise, get the pads replaced (or DIY). Once the rotors get scored, the job gets a lot more expensive.
 

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Discussion Starter #11
The outer CV/axle to hub nut and spline back-lash would be a one time click. Once on regen deceleration or reversing, once on forward acceleration, but not repeated, not "thumping" nor "rumbling". Tightening the outer axle to hub nut could (as I did to both of my axles) correct a one time click at the change from decel to accel, but won't do jack for a rumble. Noise from the front end? Tighten the nuts. When all you have is a hammer, everything looks like a nail.

Here's where the big problems with the use of "L" mode as a cause of inner joint failure are:

Regen is limited to some maximum deceleration rate, some maximum number of kW. That limit is LESS than the 100+ kW of acceleration. You simply can not apply more regen braking torque into the axle than the forward torque of acceleration applies.
Any braking force needed above this is applied by the hydraulic friction brakes located at the outer end of the axle on the Volt. Some cars have inboard brakes and these do apply braking force through the axle to the wheel/tire, but not the Volt.
Use of L rather than D does not increase the limit of that regen. It only applies harder at any given point, but does not exceed that factory set limit. The foot brake pedal, in D, can apply regen from zero kW to the max limit. The use of L causes that to be, I dunno, 20 kW(?) up to the same max limit. In either drive mode the max braking load that can be applied through the axle is less than the 100+ kW maximum forward drive load.

The inner joint may well be worn, but it isn't due to regen braking.
Inner joints, and outer joints, too, will wear. They wear based on their direction of frequent use. The contact surfaces used in forward movement have more use than the contact surfaces used in reverse (or regen). Eventually this leads to rumbling as the amount of play between the forward and reverse contact surfaces increases as those surfaces erode. SAAB used to (mid-60's) suggest in their factory service manuals to swap the complete (equal length) left and right axles side for side to extend intervals between replacements. Although this only moved the worn and 'noisy' forward drive surface of the joints to the reverse side, the opportunities of detecting "rumbling" at 30 mph in reverse are much less.

If the inner joint boot was damaged (cut, split, chemically softened, pinched during install or service) allowing grease contamination, or if there were insufficient grease as assembled, that I'd believe could lead to an earlier than expected joint failure, but 45k mile failure, on an inner joint, is NOT caused by use of "L".
No, the boots, they said, were intact and the grease packing was ok. I dunno, but I do know that 44k (it would have been earlier, actually, before detection) is far too early for a CV/axle failure due to wear. I still remember my 1985 Audi 5000 having a boot replacement with still-good joints at well over 150k). Just to be safe, I'm going back to D. The miniscule amount of battery/gas saved with L isn't worth it for me. It was fun for a while, but whatever. I'm getting too old for fun if it means swapping a $750 axle every 35-40k.

And for the record, the last car I remember with inboard brakes was the magnificiently quirky Alfa Romeo Milano that had a deDion rear suspension with inboard brakes. I so wanted my parents to buy one of those but apparently my father was too lame (and smart enough) not to.
 

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Well, this thread has me concerned. I've had my 2014 Volt for 5 years, has 35K miles, and I drive exclusively in L. The only car trouble I've had was the 12V battery died a couple years ago while I was away on vacation. I've had the oil changed once. The original brake pads have started to squeal at very low speeds while cold, so I figured I'd need to get the pads replaced at the next maintenance visit. $200 a wheel? How is that possible? Is that including replacing the rotor? I'd better get the pads replaced before the rotors gets damaged.
Just have the pads removed and scuffed on some flat concrete to break the glaze then reinstall. Don't have the rotors resurfaced or you'll lose the anti - rust coating.

Pro tip: excessive use of tire shine and wheel sprays will contaminate the pads and cause glazing and noise.
 

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I stumbled on this thread, but I did have to replace my CV shafts on the volt. We have 149K on our 2012 so I figure that is normal maintenance. We had the exact same symptom of continuous clicking on decel and turning. Especially bad when turning into a driveway as an example. Limited to no noise on accel. Ran it for probably 10k miles before doing anything about it and no issues. I replaced both sides with aftermarket axles (ordered from autozone). They were about $100 each, so the dealer price is pretty insane. I'm pretty sure our Passenger side went out first and when i replaced that the drivers side got louder. I also replaced the end links while I was in there. It fixed the continuous clicking/clunking, but now we have a single click/clunk on accel. I might be a little low on trans fluid from removing the driver side axle.
 

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156k miles on my 2012 always driven in L. No axle issues and still haven’t replaced the brakes. They will look nearly perfect after a check this last weekend.

L and learning the regen distances means I can nearly come to a dead stop. Press brakes at 10mph most times if need to fully stop and that doesn’t take much wear on the pads.
 

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Everything I have read says driving in L is no big deal- its all software. My 2014 has 70k miles with no axle issues and I always drive in L . L in Volt is like regen in Teslas and other EV's. Regen braking is part of owning an EV. The normal D mode is in the Volt so people who aren't use to regen braking don't flip out. L saves brakes, is safer in traffic and gets you more electric miles.
 

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Everything I have read says driving in L is no big deal- its all software. My 2014 has 70k miles with no axle issues and I always drive in L . L in Volt is like regen in Teslas and other EV's. Regen braking is part of owning an EV. The normal D mode is in the Volt so people who aren't use to regen braking don't flip out. L saves brakes, is safer in traffic and gets you more electric miles.
I agree. D will use regen when you mash on the brake pedal, up to the limit of how much the generator and battery can soak up. The only reason I don't use L very often, is on my 2014 you don't get brake lights when you let off on the gas pedal in L, but you do when you touch the brake pedal in D, so I consider D safer for driving, because of reduced chance of getting rear ended in D.
 

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156k miles and all in L. Never an issue to be rear ended when taking foot off the brake. I assume it throws people off some to come to nearly a full stop before they see my brake lights come in when I finally press the brake pedal.

Plus helps to get those following closely off you as they will quickly drive around you when you are in L and let off
 
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