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Discussion Starter #1
I typically drive in L, so I'm very used to the ambient sound and fury of the Voltec drive. Tonight, though, there was a lot of sound when coasting - definitely speed related. I can hear it a little when driving forward, but road noise masks it pretty well. This is new behavior that started on my drive home this evening.

I called into OnStar and asked for diagnostics, but nothing came up. Also, no CEL. I'm firmly convinced its the main drive and regen related - coasting in N has no sound, so it's not brakes or wheel bearings. Putting gear shift into D brings the return of the whine, and L brings it on faster.

Car's going into the shop tomorrow, but any thoughts are welcome. I'll post a follow up when I learn something from the dealer...
 

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One possibility could be a worn gear from the regenerating electric motor is making noise when under reverse (from the regeneration) torque. I have heard worn manual transmissions that had that happen. Of course, I have also heard high performance flat cut gear transmissions that did that new and were considered "normal".

But the Volt should not do that, hope Chevrolet fixes it for you.
 

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I and another board member had a sound that was very accurately described as "the sound a table saw makes when you turn it off". For me it started very subtly but within 1000 miles got VERY load. I don't remember the exact part but it was a motor bearing. The part was in very short supply but my dealer was able to bid on one from another dealer. The other person had to wait many days for the part..

The problem has not resurfaced in the 2 months since it was fixed
 

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Discussion Starter #5 (Edited)
High pitch (inverter) whine or more mechanical?
Mechanical. My gut says a bearing that is failing, and the reverse direction stresses it more. My guess is that bearing is in the main traction motor-generator. Pitch changes as a function of speed, and at low speed it's pretty low.

I'll find out soon enough, I guess.
 

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Discussion Starter #6 (Edited)
I and another board member had a sound that was very accurately described as "the sound a table saw makes when you turn it off". For me it started very subtly but within 1000 miles got VERY load. I don't remember the exact part but it was a motor bearing. The part was in very short supply but my dealer was able to bid on one from another dealer. The other person had to wait many days for the part..

The problem has not resurfaced in the 2 months since it was fixed
That's a pretty good description of this sound, confirms my initial reaction. it probably has been growing, but it definitely got loud yesterday.

Other than waiting on a part, is the repair itself difficult? Did you write this issue up on the forum? I'll go do a search, but we all know how effective searches are... [edit: found it - here - now I have to read it more completely]
 

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Discussion Starter #7
Quick update: a failed stator bearing. Waiting on parts to be delivered tomorrow. If all goes well, I'll have my Volt back tomorrow evening.

The service advisor says that there's a plastic element separator that seems to fail and then it all gets ugly.
 

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I have listened to the mp3 and I have a similar sound. I currently only hear it with the windows down, no stereo, L regen slowing down from 25mph to 0.

When you get your car back please let me know if you hear anything during similar circumstances. I have attached an audio clip, this was taken with my iphone holding it outside over the a pillar. While not that loud, it sounds the same.

View attachment Voild_Regen.zip
 

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Quick update: a failed stator bearing. Waiting on parts to be delivered tomorrow. If all goes well, I'll have my Volt back tomorrow evening.

The service advisor says that there's a plastic element separator that seems to fail and then it all gets ugly.
Let us know what they replaced. Last time I heard about this one they replaced the whole motor.
 

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Discussion Starter #10
Let us know what they replaced. Last time I heard about this one they replaced the whole motor.
Just spoke with advisor. Bad news first, still waiting on some parts. Monday, *MAYBE*. I'll spend more on gas for the Cruze in 5 days than I spent the last 4 months on the Volt if it keeps up this way (oh, but I have to count the electric savings - 0.50/day for 5 days ;)).

More factual news: Along with some of the seals and the bearing itself, the cover over M/G B also has to be replaced. Seems that when the bearing goes, the stator moves/can move inside the case and damages the cover. More mysterious behavior that may make sense to others, but based on diagrams I'm looking at, I'm real sure that I don't get it.

I asked the advisor to let me look at the parts, but he seems unwilling. He is going to take some pictures - if I get them, I'll share here.
 

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Discussion Starter #11 (Edited)
Here are the pictures I received from the advisor. What's interesting is the apparent construction of the bearing - it seems that there are groupings of balls separated by this plastic spacer. The grouping effect might be an artifact of failing; somehow I anticipated that that balls would be evenly distributed about the bearing to unify the load.

Anyways, here's what I believe the images represent:
  1. ResizedImage951350678807010.jpg Fuzzy shot of inside of A/Trans Case Cover Assembly - cover over M/G B. Also shown is the bearing (removed from the cover) and the plastic separator cage (tan, about 3 o'clock on the cover).
  2. ResizedImage951350678787061.jpg Close up of the plastic separator cage.
  3. ResizedImage951350678767655.jpg Close up of the bearing - you can see the grouping but what I see best are the gaps and non-uniform distribution of balls.
  4. ResizedImage951350678703528.jpg Inside of trans assembly, looking at the top of the M/G B rotor. Apparently nothing here is damaged from the failed bearing.

No update today on parts status. BTW, the Cruze is a poor substitute for the Volt. Must be true, my wife said so last night.
 

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Discussion Starter #12
Final result - my car was returned to me on Monday evening. It's all quiet again.

I got a chance to talk to the mechanic. He said that he didn't get why it was a plastic cage, but the one he get to replace the dead one had what appeared to be a brass cage. Further, he said that this bearing is not something he could order from the parts department - it had to come special from the Volt support team.

I'm very happily rid of the Cruze - I could barely afford it! 322 miles, 29.9MPG average = 10.76 gallons of gas consumed (as a point of reference, May-October in my Volt was 9.0 gallons of gas).
 

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Thanks very much for the pics and description. My 2011 Volt was dropped off at the dealer last week for the same noise/bearing issue. Lots of phone calls from GM...
 

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How much more quiet is it? With the window down can you still hear similar sounds under heavy regent?
 

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Went to the dealer today to test drive a 2013 volt, no noise at all under heavy regen. Mine on the other hand, makes the table saw noise. Looks like I will be going in for a dealer visit.
 

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Here are the pictures I received from the advisor. What's interesting is the apparent construction of the bearing - it seems that there are groupings of balls separated by this plastic spacer. The grouping effect might be an artifact of failing; somehow I anticipated that that balls would be evenly distributed about the bearing to unify the load.

Anyways, here's what I believe the images represent:
  1. View attachment 7724 Fuzzy shot of inside of A/Trans Case Cover Assembly - cover over M/G B. Also shown is the bearing (removed from the cover) and the plastic separator cage (tan, about 3 o'clock on the cover).
  2. View attachment 7721 Close up of the plastic separator cage.
  3. View attachment 7723 Close up of the bearing - you can see the grouping but what I see best are the gaps and non-uniform distribution of balls.
  4. View attachment 7722 Inside of trans assembly, looking at the top of the M/G B rotor. Apparently nothing here is damaged from the failed bearing.

No update today on parts status. BTW, the Cruze is a poor substitute for the Volt. Must be true, my wife said so last night.

This is worrying me :( plastic cages in bearing in various automotive applications over the years have failed :( why on earth would they use plastic cages here instead of metal? To save $1 on a $44k car? Any Chevy reps on here care to comment? I guess the good news is this is covered under the 100k power train warranty...
 

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Very strange to use plastic parts in ball bearings. They will all slowly break down over time, either chemically or due to temperature. The engine internals are just not a friendly environment.

When I took off the front wheels of my Volt I discovered another plastic part that slightly worries me for the same durability reasons. Its a 1-foot long linkage arm that connects the shock absorber assembly to the torsion bar that links the left and right front wheels. Its the first time I saw a plastic suspension part. Its one that is taking quite a beating in regular use.
 

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The separator may be nylon. The right grade of nylon can be as tough as steel. I believe GM tested nylon rear differential gears in taxis running in New York many years ago.
 

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I am a working auto tech and see sway bar links (the parts you are refering to) plastic in many cars. Even high end cars. Don't sweat it. It's the joints at the end that go bad. They have metal inside. I have inspected my Volt's suspension system and it resembles the normal system GM has used for years. It will perform just fine but do expect front wheel bearings, tie rods, ball joints, and sway bar links going bad as the car ages. The 40K price is for the powertrain technology, not suspension. I'm OK with it.
 
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