This makes the assumption that they're related. Tesla states otherwise. Did you get some kind of feedback from them saying that the milling sound was related to your DU issue?
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100% drive unit failure rate??
- Thread starter yobigd20
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- Driving Dynamics Model S
This makes the assumption that they're related. Tesla states otherwise. Did you get some kind of feedback from them saying that the milling sound was related to your DU issue?
In this thread a week or so back someone said they had learned from someone in Tesla the milling noise is caused by micro-pitting in the ball bearings caused by improper current paths that pass through the bearings. That was before Elon Musk talked about the grease injectors during the investor's call, but they may not be talking publicly about current paths. People who don't understand the entire issue might jump to the wrong conclusion that people could get electrocuted from current going the wrong places and that would become a PR headache for Tesla.
If there is micro-pitting going on in the ball bearings, the problem might be originating due to a problem with electrical ground paths in the car's chassis, which would explain why some cars have recurring problems and others never have any. It could also explain why some cars have milling problems developing at shorter and shorter intervals.
Edit: I came across this after my last post:
Tesla Model S Drive Unit Replacement by the Numbers - TESLARATI.com
The information originated in polls here, which is not a scientifically valid sample, but it's the best info I've seen.
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JRP3
Hyperactive Member
Which is likely not correct since Tesla uses ceramic bearings which don't provide current paths. The more likely answer, from the article you linked:
No one outside of Tesla has the data to come to a logically supported explanation of what causes the "milling" sound. Everyone outside of Tesla is speculating as to the cause. Tesla is not obligated to provide an explanation, the company is only obligated to fix the issue when it occurs. In some cases, like @Islandbay and a few others, Tesla does not appear to be succeeding in fixing the issue. That is definitely a problem. In many other cases Tesla does appear to be fixing the issue. I am confident that over time Tesla will solve the problem. Obviously, it has to be solved.
In the meantime, no doubt the speculation will continue. But it should be described as speculation.
In the meantime, no doubt the speculation will continue. But it should be described as speculation.
The way to find out would be to find a Tesla that has been totaled and was known to have the milling sound prior to the accident, then ship the drive unit to a lab and get an analysis. Of course, that would require money and knowledge of the particular car.
If this was specific to the vehicle causing the DU to fail, wouldn't we have heard something along those lines by now? And if so, why is Tesla focusing solely on the DU design? There are three different issues, I believe: highway hum, milling noise, and inverter buzz. Reports of highway hum were numerous in 2013 and 2014, but seem to have trailed off. Now most of the posts are regarding milling noise. The lack of posts regarding highway hum would seem to indicate that issue was resolved. Very few, if any, reports of inverter noise/buzz so that may have also been resolved to a large extent. Milling noise seems to be the most prevalent issue in the forum today, and that has most likely been resolved in whatever new DU goodness Elon was discussing during the earnings call.
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I don't believe Tesla ever said anything like this. As others have pointed out, Tesla uses ceramic bearings. One owner here in the forums had hypothesized this was the issue, but that was his own hypothesis and not something put forth by Tesla.
FredTMC
Model S VIN #4925
Ceramic bearings in Model S rear DU motor? Where did you hear this?!
someone stated earlier that the Roadster had them but NOT Model S. I believed him... Seemed very knowledgeable. For example, he knew who the original motor designer was and that he already left the company.
JRP3
Hyperactive Member
stopcrazypp
Well-Known Member
Because this a complex issue that has many possible causes? By the same logic, if it was a simple issue, Tesla should have solved it by now. That they haven't yet shows there is something Tesla is missing. There are definitely examples where people have gotten the newest revision and actually have them last a shorter time than the ones they previously had. That suggests in their specific situation, it may have something to do with their specific car and I would hope Tesla does not just dismiss that possibility outright in investigating the causes. Note, I am not saying that this applies in general to all cars with the issue or even a large portion of cars, but I am saying that in specific cases it might just have to do with the car itself and not the DU.
SW2Fiddler
We Are Cognitive Dissidents
I developed a square-wave buzz in my April 2014 S85. More audible above 8MPH due to more power in the hi-frequency harmonics, but decidedly only present during discharge, any discharge however slight. I just mentioned it offhand to the valet, didn't ask for anything to be done about it since it wasn't a Milling type sound.
SvC replaced with a reman M drive unit and put "milling noise" on the warranty invoice.
More than one condition is obviously being labeled "Milling Noise" and this is not going to help our speculative diagnostic efforts, at all. It would be Job 1 to differentiate between mechanical noises and electronic ones like mine.
SvC replaced with a reman M drive unit and put "milling noise" on the warranty invoice.
More than one condition is obviously being labeled "Milling Noise" and this is not going to help our speculative diagnostic efforts, at all. It would be Job 1 to differentiate between mechanical noises and electronic ones like mine.
thegruf
Active Member
Actually this might not necessarily be true.
If the gear that the DU spline is connecting to is out of alignment or itself has a vibration at speed this theoretically could cause a repeated wear issue.
Theoretically of course as I for one, and I suspect nobody outside Tesla really know the root cause(s) of DU failures.
JRP3
Hyperactive Member
The drive unit consists of the motor, inverter, and transaxle. All connections between them are self contained. If a spline is out of alignment that's a problem in the drive unit, not the car.
I assume you're talking about sending the unit out to an independent lab for analysis. I'm sure Tesla has taken apart many DUs with noises to figure out what was causing it.
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Good analysis of the types of problems. I thought the person who said it was the bearings said it came from someone at a service center, but I could be wrong and I can't find the post at the moment.
I watched the video posted on insideevs. I note Jim Seta said one set of bearings were SKF ceramic bearings. Though I don't know where the other bearings would be.
There is someone in Europe who has been hacking the motor and figuring out how to control it with different electronics, but I don't know of anyone who has take a DU apart. The guy with the motor hack:
https://www.youtube.com/watch?v=zMQjcukphpA
If the bearings are non-conductive there goes my theory. It still leaves the question open why some cars develop problems after a short time while others never have any problems. What's different about the car itself that a brand new drive unit would start developing noises in a very short time?
Yes, I started hearing milling noise several weeks before the failure. Is it related? Who knows.
What is more worrying - the breakdown happened exactly two days after a scheduled service (12500 miles). I had a couple of small issues for that service (wind noise, a couple of rattles, window catching on the chrome trim) but forgot to mention the milling noise. It seems that Tesla service centers do not even have tools to evaluate the current vehicle state.
So personally, I'll now be treating any milling noises as an imminent breakdown warning.
Regarding cars being prone, I wonder more about machine defects in the rebuilt motors that make new bearings doomed. Maybe design tolerances being too broad? Could a concentric flaw in the motor casing be thrashing the bearings? The onion was probably peeled well past this, by now. This just adds speculation, but my point is to consider that flaws may exist in the sample DU parts they are stock piling, and putting back together. That would lend itself to the reported repeat offenders.
JRP3
Hyperactive Member
We don't know when that drive unit was built and we don't know if Q is the latest revision. They may be full of it but I don't see this as proof. It certainly is a bit of a cluster...
Given that islandbayys DU was ordered directly from Fremont I think we can reasonably conclude it was the best available unit at time of install.
JRP3
Hyperactive Member
Yes, my point is that the newest units may be going into production vehicles and may not yet be widely available for replacements. If in fact these are the latest and greatest and still aren't solving the problem that would be tragic.
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