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94K views 118 replies 68 participants last post by  hellsop 
#1 · (Edited)
Compiled from various GM-Volt threads. The questions below are answered in a numbered section lower on the post.

  1. I have started to notice a sound progressively getting louder when I brake and Accelerate but mostly very loud when I am stopping. It sounds like a table saw winding down. This is something that never happened before. What is causing this?
  2. What kind of damage can I cause by driving the car with this issue?
  3. Do I need to have the car towed to the dealer?
  4. Is there a service bulletin I can refer my Chevy dealer to? Yes, PIP5081H
  5. What tools are needed by the dealer for the repair?
  6. How difficult is the bearing repair?
  7. Does the repair require removing the transmission?
  8. Does the rotor need to be replaced in addition to the bearing cage?
  9. Does the entire MG-B rotor/stator assembly need replacing?
  10. Once repaired, can the bearing fail again?
  11. What if the bearing noise problem persists or returns after repair?
  12. What causes the bearing to fail?
  13. Is failure of the bearing related to driving in Low? Number of miles? The car year?
  14. Is failure of the bearing common?
  15. If this bearing failure happens outside the warranty, will it be expensive?
  16. How is the whining or table saw noise being created?
  17. Why is the whining sound louder during regenerative braking?
  18. Based on the noise, I believe the damage is much greater than this FAQ seems to imply.
  19. Why was repairing this bearing failure such a big deal initially?
  20. Is this a warranty repair? What about the extended warranty?
==================

  1. I have started to notice a sound progressively getting louder when I brake and Accelerate but mostly very loud when I am stopping. It sounds like a table saw winding down. This is something that never happened before. What is causing this?
    This sound could indicate a bearing race failure. Symptoms? It sounds terrible – like a saw blade slowing down. A slight ticking sound in reverse, more sound in Drive and even louder in L – the pitch increases with speed, but gets louder at lower speed.

    http://www.youtube.com/watch?v=F2ulyuyBVE8

  2. What kind of damage can I cause by driving the car with this issue?
    If it is a bearing cage failure, it sounds a lot worse than it is. It DOES NOT come into contact with the stator nor does it grind up the core into pieces, nor does it damage the stator. Take it to the dealer. It shouldn't really be a problem driving it another 18 miles (30km) but you can contact OnStar and have it towed to be safe and minimize any collateral contamination (just plastic debris for the most part).
  3. Do I need to have the car towed to the dealer?
    It shouldn't really be a problem driving it another 18 miles (30km) but you can contact OnStar and have it towed to be safe and minimize any collateral contamination (just plastic debris for the most part). There is no serious damage as long as it's dealt with expeditiously. But since the appearance noise is so sudden and obnoxious to your average Volt owner, that really isn’t a problem.
  4. Is there a service bulletin I can refer my Chevy dealer to?
    Yes, have them look up and read the PIP5081H and the replacement procedure in GM's Electronic Service Information system BEFOREHAND. Also make sure they have the proper tools at hand.
  5. What tools are needed by the dealer for the repair?
    These ARE NOT Volt specific tools!
    DT-47865 - Bearing Remover and J-45124 - Removal Bridge
    http://gm-volt.com/forum/attachment.php?attachmentid=40186&d=1385435849
    DT-22928-B Bearing & Seal Installer
    http://gm-volt.com/forum/attachment.php?attachmentid=40178&d=1385435848

  6. How difficult is the bearing repair?
    It's really no different that repairing a conventional automatic transmission (which is FAR more complicated that the internals of the Volt's drive/propulsion unit by the way) in that many can be repaired without completely overhauling the entire unit. This is really no different. BUT it requires the right tools and a trained tech willing and able to follow the published processes for the repair.
  7. Does the repair require removing the transmission?
    The repair is typically done in-car through the LH fender well while the car was up on the lift - all open from underneath (the fender itself isn't removed).
  8. Does the rotor need to be replaced in addition to the bearing cage?
    Rarely. Early on, the rotor was been replaced in a handful of Volts either due to the unavailability of the bearing itself (originally this bearing was not to be a serviceable part i.e. part of the rotor), or unavailability of the special tools needed to properly remove and reinstall it. A bulletin now clearly identifies how to replace the bearing and the correct tools to use. The rotor was also replaced on a couple of cars that had a repeat failure after the bearing alone had been replaced at the dealership.
  9. Does the entire MG-B rotor/stator assembly need replacing?
    Replacing the MG-B rotor/stator assembly really isn’t necessary for the repair to be successful. Instead, it's more an alternative method to obtain a pre-installed bearing in the event ordering the individual part, or the tools necessary to service it cannot be obtained in a timely manner.So the dealer would be well advised to insure they have the tools and parts on-hand BEFORE tearing the drive unit apart. They should look up and read the PIP5081 and the replacement procedure in GM's Electronic Service Information system BEFOREHAND.
  10. Once repaired, can the bearing fail again?
    Possibly, though this is not a chronic issue. Essentially ALL of the repeat failures have been attributed to the repair procedures NOT being followed by the technician. If the Chevy service tech failed to look up or read the PIP5081 and the replacement procedure in GM's Electronic Service Information system BEFOREHAND this could certainly cause a substandard repair and subsequent repeat of the problem. So, there's not much chance of a repeat failure, providing the bearing was properly replaced, as in the technician carefully followed the published process for it's removal and installation. If for whatever reason they do not (e.g. didn’t have the correct tools, or didn’t use them correctly, didn’t follow the detailed instructions for R&R or measuring the bearing race for proper alignment after it's installed, and a couple of additional inspections necessary to insure it's fixed right the first time. etc. etc.) then the repair might NOT be a success, especially if the noise does not alleviate (or returns after a short period of time).
  11. What if the bearing noise problem persists or returns after repair?
    Get your Volt Advisor involved. There's not much chance of a repeat failure, providing the bearing was properly replaced, as in the technician carefully followed the published process for it's removal and installation. If for whatever reason they do not (e.g. didn’t have the correct tools, or didn’t use them correctly, didn’t follow the detailed instructions for R&R or measuring the bearing race for proper alignment after it's installed etc. etc.) then the repair might NOT be a success, especially if the noise does not alleviate (or returns after a short period of time). If the dealer tech had some sort of trouble replacing the bearing they MAY need to replace the complete rotor (comes with the bearing) or even the drive unit assembly in order to remedy the issue.
  12. What causes the bearing to fail?
    Damage to the bearing race during final assembly of the drive unit.
  13. Is failure of the bearing related to driving in Low? Number of miles? The car year?
    No. There is no correlation with driving in Low, or in Drive for that matter. Very few of these have actually occurred and the issue has been identified as potential damage to the bearing race during final assembly of the drive unit.
  14. Is failure of the bearing common?
    No, but it is concerning for those who experience it.
  15. If this bearing failure happens outside the warranty, will it be expensive?
    It's not a difficult or even an expensive repair. The drive unit does not need to be removed. Assuming everything (tools, parts, repair bulletin) is "at hand" it shouldn't take longer than 3-4 hours. Not much more than an old-school tune-up...
  16. How is the whining or table saw noise being created?
    The noise is created by the fact that after the plastic roller cage fails some or all of the bearing rollers are no longer properly/equally spaced around the circumference of the rotor support in the end cover. The rollers are all still there, as they are "captured" within the bearing races but will "gather" together and spin inside the races at what is now an un-natural frequency. This is what creates the “whining” or “table saw” sound. This bearing (as with all ball/roller/needle bearings) is designed for metal to metal contact, within the confines of its races providing there is adequate lubrication (the bearing is pressure fed transmission fluid from an internal passage) so there isn't really any serious metal contamination present OR any damage where on the 2 parts in which the bearing is working in conjunction with- just a noise and a bunch of plastic material scattered through the end cover.
  17. Why is the whining sound louder during regenerative braking?
    The noise is more pronounced during regen because the magnetic fields created between the rotor and stator windings during regen are quite strong which creates certain thrust forces that actually move with the active poles involved, and therefore placing fluctuating loads on the bearing. So technically the noise it ALWAYS there but merely becomes more pronounced under these conditions.
  18. Based on the noise, I believe the damage is much greater than this FAQ seems to imply.
    There's always going to be a few skeptics when someone tells them it sounds worse than it actually is. But there is no serious damage as long as it's dealt with expeditiously.
  19. Why was repairing this bearing failure such a big deal initially?
    There weren't any spare parts or repair procedure. Someone made an educated decision at some point that this particular bearing was not something that would ever require routine replacement (other than when the rotor was replaced). They were obviously wrong in that decision.
  20. Is this a warranty repair? What about the extended warranty?
    The bearing repair is certainly covered under the 3 year/36k bumper to bumper warranty. It seems to me it would also be covered under the 5 year/100k mile power train warranty (the engine, the transmission/transaxle, and the drive train). Any Voltec componenet is covered 8 years/100k miles, but I don't think the bearing would be considered a Voltec component. A GMPP Major Guard warranty extension covers
    "Virtually every mechanical, electrical and electronic component of your vehicle is covered against failure even if it results from wear and tear *. You're covered for parts and labor on:
    Engine
    Transmission / Transaxle
    Front / Rear-wheel-drive components
    Fuel delivery component
    Engine cooling component
    Heating and vehicle manufacturer-installed air conditioning components
    Electrical, computer and audio components
    Braking system components
    Suspension (Front / Rear)
    Steering component
    High-tech components
    Seals and gaskets
    Safety components
Sources:
http://gm-volt.com/forum/showthread.php?66482-Bearing-Failure-vs-Driving-in-L
http://gm-volt.com/forum/showthread.php?89658-Another-Motor-Bearing-Failure
http://gm-volt.com/forum/showthread.php?85658-Stator-Bearing-Failure
http://gm-volt.com/forum/showthread.php?56705-GM-fix-my-Lemon-take-2...
http://gm-volt.com/forum/showthread.php?46489-Fix-my-Volt-Please-Take-1.
 
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#9 ·
The bearing repair is certainly covered under the 3 year/36k bumper to bumper warranty. If it's considered part of the power train—the engine, the transmission/transaxle, and the drive train—(seems like it is part of the power train to me), that warranty is 5 years/100k miles. Any Voltec componenet is covered 8 years/100k miles. I don't think the bearing would be considered a Voltec component. A GMPP Major Guard warranty extension of that would seem to apply as it covers
"Virtually every mechanical, electrical and electronic component of your vehicle is covered against failure even if it results from wear and tear *. You're covered for parts and labor on:
Engine
Transmission / Transaxle
Front / Rear-wheel-drive components
Fuel delivery component
Engine cooling component
Heating and vehicle manufacturer-installed air conditioning components
Electrical, computer and audio components
Braking system components
Suspension (Front / Rear)
Steering component
High-tech components
Seals and gaskets
Safety components
 
#6 ·
Some mild, almost inaudible whine is normal at low speeds when the car is starting out or slowing. At least, I hear some. Not objectionable or bothersome, though I suppose some with more sensitive hearing may hear more or be bothered. A bearing failure leaves no doubt in the driver's mind that something is very wrong. Dogs start howling and pedestrians will turn to see where the noise is coming from. It's not a subtle thing.
 
#5 ·
Thanks Steverino, puts all those "myths" finally to bed .....

Just wish GM should have put this out at the start, also agree if Tech's don't do it right then it comes back as a boomerang.
(Transmision and bearing replacement work isn't for all techs), seen some locally - cannot even get a race into a wheel hub properly seated - locally like my local Ford dealership!. But there are also some that have a brain - keep things clean and know how to install bearings to seat them evenly unstressed. great info...!

Great info!
 
#7 · (Edited)
I'm surprised this is still a problem, even if in low numbers. It should be resolved by now!

EDIT: By the way, nicely done on the FAQ though :)
 
#10 ·
Thank you so much for this post! I just dropped my Volt off at the dealership on Friday because of this whining. I came home and researched it on the internet and thought it was most likely the bearing. The dealership confirmed on Monday. You have answered all my questions except does anyone know what percent of all Volts have had this issue? Is it rising to the level of a recall? (My Volt is a 2012 w/ 38k)
 
#12 ·
Thank you for your explanation. It was timely because I had just taken my 2012 Volt, 38k, to the dealer for this problem. It was fully covered under warranty and they even paid for a rental car for me as I live 1 hour away from them. They part was ordered on Monday and arrived on Wednesday. The car was fixed on Thursday. They were generous and let me keep the rental until Friday when I could make it back up. Your explanation was greatly appreciated and gave me the info I needed to feel knowledgeable.
 
#14 ·
Do I need to have the car towed to the dealer?
It shouldn't really be a problem driving it another 18 miles (30km) but you can contact OnStar and have it towed to be safe and minimize any collateral contamination (just plastic debris for the most part). There is no serious damage as long as it's dealt with expeditiously. But since the appearance noise is so sudden and obnoxious to your average Volt owner, that really isn’t a problem.

What if the bearing noise problem persists or returns after repair?
Get your Volt Advisor involved. There's not much chance of a repeat failure, providing the bearing was properly replaced, as in the technician carefully followed the published process for it's removal and installation. If for whatever reason they do not (e.g. didn’t have the correct tools, or didn’t use them correctly, didn’t follow the detailed instructions for R&R or measuring the bearing race for proper alignment after it's installed etc. etc.) then the repair might NOT be a success, especially if the noise does not alleviate (or returns after a short period of time). If the dealer tech had some sort of trouble replacing the bearing they MAY need to replace the complete rotor (comes with the bearing) or even the drive unit assembly in order to remedy the issue.

What causes the bearing to fail?
Damage to the bearing race during final assembly of the drive unit.

Why is the whining sound louder during regenerative braking?
The noise is more pronounced during regen because the magnetic fields created between the rotor and stator windings during regen are quite strong which creates certain thrust forces that actually move with the active poles involved, and therefore placing fluctuating loads on the bearing. So technically the noise it ALWAYS there but merely becomes more pronounced under these conditions.
Are there some things that need updating here?

There seem to be many examples now of second, brass, bearings failing. Consequently, rather than plastic pieces in the box, this will lead to metal fragments. Pretty bad, no? (Are there any photos of the failed brass bearings?)

If the reason for the thing is damage to the race, what damage is done to the brass race, and why/how does it get damaged in the same way? (Metal would bend and dent and doesn't soften, where plastic would crack and chip and soften with temperature.)

On the latter point I requoted, so are we sure that there is always this noise present that propagates via the bearings, or is it meant to be totally silent, as suggested by a few folks?
 
#15 ·
Most all cases of 2nd failure have been attributed to issues created during the service procedure. Most notably not using the proper tools (or not using them as outlined) or possibly the failure to properly clean debris/contamination created from the initial bearing failure and the recommended use the GM transmission flushing equipment afterwards. In most cases the 2nd failure results in a replacement of either the rotor assembly or the entire drive unit.

WOT
 
#17 ·
Thanks for this FAQ, Steverino.

I have kept an ear out for this issue since I bought my 2013. At around 40k miles I started to hear the sound and thanks to the video recordings members have captured I was able to determine my bearing was on its way out.

At 45k, I took it to the dealer, John L. Sullivan, and they took care of it plus the other 3 updates listed for my VIN and it was in the shop for 1.5 days. Not bad considering they had to order the bearing. The turn around period seems much reduced nowadays so if you are experiencing a problem I'd suggest getting it checked out sooner rather than later. I avoided it because I thought my car would be down for weeks.

Thanks again for everyone who has contributed to this Knowledgebase.
 
#21 ·
OK, so this is useful FAQ material I believe....

I have had the bearing replaced on my Ampera after all, at 70k miles, even though I felt it was 'within norm' the tech said it needed replacing. I was persuaded because I have heard a colleagues Ampera which is clearly quieter than mine.

This post has a sound recording, taken under the bonnet prior to the replacement; http://gm-volt.com/forum/showthread...s&p=2376090&highlight=bearing+pdf#post2376090

I explained what I felt were the reasons for the noise and predicted all the bearings were still in their proper place and that perhaps this was a brass-caged bearing and that these are a little noiser naturally. He said the cause of the noise was the cage failure and the balls grouping up.

Job has now been done and guess what - my car did have a brass cage, and all the balls were in the right place. He said the bearing was, still, running roughly so has a new bearing now, but from inside the car I can hear no difference at all.

I think there is a fair conclusion that can be drawn;- brass caged bearings *do* run noisier than nylon. Evidently they run sufficiently noisy that it can persuade a tech to replace it.

I don't think the replacement was necessary. One thing that does concern me is his comment that the bearing was running roughly.

Is this the compromise GM had to make? Either a nylon cage that was quiet but lasts longer as long as it is running properly, or a brass caged bearing that might begin to run rougher over time?

So be aware that your car might never run as quietly as it once did with the nylon caged bearing once it is replaced.

One surprise I have, and it worries me a little - the bearing was fitted with grease packing. Are these supposed to be greased bearings? I though the ATF did the lube for the bearings, no need for grease? What does the Bulletin on replacement say to do?
 
#24 ·
OK, so this is useful FAQ material I believe....
I have had the bearing replaced on my Ampera after all, at 70k miles, even though I felt it was 'within norm' the tech said it needed replacing. I was persuaded because I have heard a colleagues Ampera which is clearly quieter than mine.....One surprise I have, and it worries me a little - the bearing was fitted with grease packing. Are these supposed to be greased bearings? I though the ATF did the lube for the bearings, no need for grease? What does the Bulletin on replacement say to do?
Thanks to everyone posting info on this. I would like to see the bulletin too and it may already be posted someplace here. The link to some tech data above didn't work for me. I'm reviewing past issues with Volts since we just bought one. and just noticed the comment about bearings. This seems to be more common in a lot of vehicles of any make. Bearings seem to have gotten lower in quality at times since the 80s. My H-Body GM cars (LeSabres mostly from late 80s) have over 200k mi with the original sealed hub bearings and never had any issues with other easily serviceable/manually lubricated parts. This Volt bearing issue might have some things in common with any sealed 'lifetime' grease packing that just never was installed or manufactured properly at the start. We may also assume some service depts under more pressure to do it faster and more cheaply will cut corners on a replacement job making matters worse.
 
#22 ·
I found some publicly available information that appears to be taken directly from the PIP5081G for anyone that wants to see some of the more technical aspects of this repair:

oemdtc.com/14015/whine-scrape-whistle-type-noise-while-driving-2011-2015-chevrolet-cadillac-opel
 
#28 · (Edited)
So after reading the attached article and some allusions in this thread to inverter induced voltages on the motor shaft, I am wondering if this is the culprit in repeated bearing failures for me.

I am looking at having to take my 2013 in for a third time to get a bearing issue fixed.

I will ask for a new drive unit in order to put this issue to rest... regardless of it being technical staff incompetence in seating a bearing properly, or permanent damage incurred during initial assembly.

https://www.ecnmag.com/blog/2012/05/bearing-damage-lurking-problem-electric-cars

Here's an excerpt:

Cause and effect
For electrical damage to motor bearings, the main culprit is common-mode voltage arising from the non-sinusoidal waveforms produced by an inverter’s power-switching circuitry. The extremely fast voltage rise times (dV/dt) associated with the insulated gate bipolar transistors (IGBTs) typically found in today’s pulse-width-modulated inverters can cause charges to build up on the motor shaft. Without mitigation, these voltages discharge through bearings, causing unwanted electrical discharge machining (EDM) that erodes ball bearings and race walls and leads to premature bearing/motor failure.

Electric motors in vehicles operate in a range from 1,000 to over 16,000 rpm, and at such speeds the very thin grease layer between the rolling elements and race in a bearing can break down due to voltage discharges of 5 to 40 volts. Every time the grease dielectric is overcome, an electrical arc through the bearing burns the grease and blasts a tiny pit (fusion crater) in the steel surface [Figure 2]. At inverter carrier frequencies of over 12 kHz, many millions of pits can be created in a very short time. This process also generates steel and carbon particles that contaminate the grease, further reducing its lubrication properties and giving it a black “burnt” color [Figure 3].
 
#29 · (Edited)
Here's another article. Perhaps this rotor shaft electrical voltage damaging bearings isn't news to you all, but it is to me.

This seems like a common issue in AC motors. In fact, Tesla's are also experiencing this issue, but apparently Tesla is solving the problem with more expensive non-conducting ceramic bearings. See: https://forums.tesla.com/forum/forums/23-drivetrains-fail-60000-miles

And here's another more in-depth article on the general phenomenon/subject: http://www.est-aegis.com/TechPaper.pdf

From the available anecdotal evidence, this very well could be at the root of the bearing failures many have been seeing. From the articles I've been reading on the subject, there seem to be two ways to solve the issue: better grounding of the rotor shaft with a washer assembly, or the use of non-conductive (ceramic) bearings. Evidence that this is the failure mode would appear as EDM (electrical discharge machining) which causes pitting in the bearings and races and contaminates the dielectric bearing lubricant.
 
#30 · (Edited)
From the available anecdotal evidence, this very well could be at the root of the bearing failures many have been seeing. .
Interesting stuff, but not the issue in this case.

The root cause is known to GM, is related to a supplier issue, and it has nothing to do with electrical activity.

If what you are summizing was the case, we would likely have many tens of thousands of failures by now (given ~120,000 cars on the roadways world-wide)

GM is also aware that repeat failures are typically an issue in the service process, and has taken steps to remedy.


Welcome to gm-volt.com
WopOnTour
 
#32 · (Edited)
One occurrence is too many

Thank you for the explanation about root cause of bearing failure being a "supplier issue".

I am on this thread due to a recent MGB bearing failure on our 2012 Volt with 72,000+ miles.
We love our car and all of the advantages EV's offer, but could someone please shed some light on:

Defining the "Supplier Issue"
a) What supplier, the 4ET50 transaxle assembly or the bearing supplier?
b) If the supplier was the 4ET50 supplier, then root cause may not be related to a single issue
but could stem from multiple sources: Bearing assembly being one factor, machined cover
or any other transmission part non-conformance.
c) If the "supplier" was the bearing manufacture then repeat failures should not occur, unless
warranty repairs were not made properly or the cause again stems to transaxle supplier.

We are not "in the know", but as owners of a Chevy Volt, we need to understand the
whole picture.

We again love our car and only want to understand it's prospects for long term reliability.

Thank you.
 
#35 ·
Give them the PI number from the FAQ post and tell them to look up the warranty coverage code on it.
 
#38 ·
Updated Service Bulletin

Hello everyone,

Thanks for your massive help in defining this issue. May I suggest an edit?

After talking to many dealers, nobody seems to know what PIP5081 is. Turns out the bulletin has a letter marking the latest revision. Has taken me about half a day of nonstop research to find this out. So far the current bulletin (as far as I can tell) is PIP5081H. I have been able to find a pdf of PIP5081D. A short google search will located it for you.

Dealerships around DFW seem to have few Volt technicians, so the car is likely going to be in the shop for a good while. A little worried they will try to tell me it's not covered under Voltec Warranty. If that's the case, all my other warranties are up.

Has anybody had this repair done recently and can you confirm that it will be covered under Voltec??

Many thanks.
 
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