Tesla Model S Drive Unit Failures/Replacements Still An Issue?

2 years ago by Mark Kane 29

Tesla Model S Drivetrain

Tesla Model S Drivetrain

Tesla Model S

Tesla Model S

The rear wheel drive versions of the Tesla Model S had some reliability issues, which in many cases led to drive unit failures/replacements.

We don’t know how many Model S  EVs suffered from the problem, but some cars got several replacements, while in Norway 1,100 were scheduled for replacement.

Some have tried to figure out the ratio of problems by launching a poll at Tesla Motors Club forum, but we feel it doesn’t provide us with clear answers.

In one of the recent articles on Teslarati, Rob M. reported on his drive unit replacement on Model S 85, delivered on April 2014. Worrying noises appeared after 12 months and 30,000 miles. A few months later (problem worsened) the drive unit was replaced and the new one is at 8,000 miles trouble-free.

Milling noises of the drive unit appear on the newer Tesla with Autopilot (you need to play it loud):


The topic isn’t trivial as we can easily find new threads at the Tesla Motors site with comments about drive units (this from October). One of them concerns a Tesla delivered December 2014 (so a fairly new car).

“Not certain on the exact cause, but my S85(Dec’14 delivery) started the “milling noise” at approx 17k miles, and I now have 27k miles. I have been on a wait list at my service center for a long-awaited factory repair, but I have not received a call yet to schedule repair. …”

The question is whether Tesla solved the drive units problem for new ones produced in 2015? Fortunately, Tesla replaces or repairs the drive units under warranty, so there’s generally no cost to the owner aside from inconvenience, but it perhaps would give a lot of Tesla owners pause as they close in on the expiry of that factory warranty.

Source: teslarati.com

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29 responses to "Tesla Model S Drive Unit Failures/Replacements Still An Issue?"

  1. Ambulator says:

    So that’s what a milling noise sounds like. I was expecting something lower pitched.

    1. martinwinlow says:

      Sounds more like a circular saw cutting wood than a milling machine to me…. and if that noise sounds like a jet engine on a ‘plane that you are in right now, get out – quick! MW

  2. Samwise says:

    A couple of things that would be interesting to know here.
    1: What piece is actually at fault, it seems unlikely to be the motor itself and there is probably a fixed ration gearing system in there somewhere.
    2: How much is this component likely to cost, in the context of a $100k car probably not that much, but something second hand buyers would likely be interested in knowing.

  3. Goodbyegascar says:

    Sounds like a jet engine.

  4. ggpa says:

    Mark, you wrote “but it perhaps would give a lot of Tesla owners pause as they close in on the expiry of that factory warranty.”

    Tesla gives an 8 year warranty for drive train. Model S has only been out for 3 years, all of them are still under warranty

    1. Jay Cole says:

      I think this is a question left up to the individual buyer and their comfort zone.

      If you had a couple units replaced and you got your car in the summer of 2012, that’s only 4.5 years to go. At what point would you start thinking about selling knowing the residuals on a 4-5 year old cars would start to more seriously take this into account?

      …or coming at it from the other side, if you were buying a used Model S at what point/age would it give you pause if this issue was on your mind? Would you buy knowing the coverage was up with less than 12 months? 24 months? 36 months?

      Not taking a side really…just an interesting question. I myself would definitely pony-up a little extra cash for every additional month of drivetrain/battery warranty (outside the actual usage/mileage of the car) available.

      1. Josh says:

        I have had that exact thought process looking at used Model Ss. I don’t really care about milage (since it is unlimited), but I would be looking for the newest possible month of build, for warranty and higher quality (based on CR study).

        I would also not plan on owning it outside the 8 year warranty. Model 3 would be out by then anyway.

  5. They really need to sort this **** out. At least the Model 3 will use totally new components; give them a chance to put a more reliable system in.

    1. Mark says:

      The model 3, being a mass market car, will likely use cheaper and less durable parts.

      Tesla hasn’t figured out how to make a lot of something or make something without durability issues, yet. I don’t predict that this problem will go away.

      1. Pushmi-Pullyu says:

        Mark said:

        “The model 3, being a mass market car, will likely use cheaper and less durable parts.”

        I’m sure there will be many places where the Model ≡ will have cheaper parts, and yes some will be less durable. But skimping on the drivetrain would be a case of “penny wise and pound foolish”. Since the Model ≡ will have its powertrain guaranteed for as many years as the Model S, Tesla will have to bear the cost of any replacements within the warranty period.

        I don’t know just what the cause is of the continuing reports of “milling noise” problems. Maybe it’s that Tesla needs to use a more robust gearing system; maybe it’s a slight mis-alignment between the motor and the gearbox (as was reported in some articles a year or two ago); maybe it’s just lack of quality control.

        But whatever it is, it does seem that Tesla should have actually fixed this by now. That they continue to have problems even with cars which have had the drivetrain replaced… well, the apparent inability to eliminate a problem so basic to the operation of an electric car would seem to cast a cloud over the future of Tesla Motors. 🙁

        1. Josh says:

          Not that I have been digging, but I have not heard of the problems with any of the dual motor systems.

          I have a feeling the new motor designs are more robust to whatever the root cause of the previous issues were.

          The first P85 I test drove (Fall 2012) had this milling noise. It didn’t stop me being blown away by the car and didn’t affect the performance at all.

    2. Bill Howland says:

      I can’t say what I really think because they’d think I was picking on them.

      Even I could design them a heavy duty gearbox (they’d have to use a slower motor, since I’m not that conversant with the synthetic oils needed at the stoopid-crazy pinion speeds Tesla uses to make the thing space-saving). My point is they might not like the SIZE of the thing I could make for them but they would like the reliability of it.

      What is discouraging here is that you’d think they’d design the thing to last 150-200,000 miles since pure EV’s supposedly last longer.

      But this is just another example of them pushing stuff too hard, and it sounds exactly like the Tesla Specific Parts on my Roadster.

      Now what WOULD be educational, is at what average mileage do the gearbox/bearings/differential, etc. SEIZE UP SOLID?

      1. ModernMarvelFan says:

        Yes, I would agree with you on this one.

        Telsa probably pushed design way too much in terms of size/weight/cost area. Maybe they have used better grade alloys, it would have helped as well but it sure would cost more…

      2. martinwinlow says:

        Ummm… except that the issue is apprently in the motor, not the transaxle. Some have suggested that the motor bearings are getting pitted due to the electrodeposition effect caused by unwanted currents flowing thought the bearings and a possible solution of using ceramic bearing components to break to circuit, as it were. But this is conjecture – Tesla aren’t saying. MW

        1. Bill Howland says:

          Well no one here is saying their design teams are idiots, because its trivially easy to eliminate inverter currents out of the bearings with a simple grounding brush on the shaft.

          The deception angle here is continuous. Musk gave the strong impression that inferior Roadster parts wouldn’t be allowed, and then quality never improved ever.

          Now Musk says the S quality has been improved, but we still find apparently newsworthy failure articles.

          There is an issue here that is not being wished away.

          1. Rich says:

            In the 3rd Quarter 2015 shareholders call, Musk was asked about the battery and drivetrain reliability targets. Musk replied that they were still working on the 1 million mile drivetrain and there was an issue with the axle grease injection system. The grease injection system was not delivering enough grease and causing undesirable wear. They’ve increased the rate of injection to resolve the issue.
            I thought the statements were specific to their pursuit of a 1 million mile drivetrain but given this article, the question takes on a different meaning.

  6. Lad says:

    My guess is the instant high torque of the electric motor is wearing the differential gears. Perhaps a slower acceleration ramp up or a better cushioning lubricant would help.

    1. Pushmi-Pullyu says:

      Certainly limiting the motor to a lower torque would help. But one of Tesla’s main selling points is the very fast 0-60 speed, and they keep getting publicity for repeatedly shaving a tenth of a second off here and there. So it seems highly unlikely they are gonna start using more limited torque in the Model S, or the X either.

      Now, the Model ≡ might well have more modest acceleration and torque. But even there, I expect Tesla to make it more than just competitive, in acceleration performance, against cars in a similar price range.

  7. Guy Dormehl says:

    Presumably Tesla will have the projected million-mile drive unit before 2020.
    As all faulty DUs are being replaced free of charge for 8 years, one would expect at some point to get a indestructible DU replacement during the warranty period. Applicable then to second hand and out of warranty cars.
    So other than the ‘marginal’ inconvenience of having the DU changed (painless from most reports), the DU issue should evaporate sometime (soon?)
    Well I sincerely hope for Tesla’s sake that this happens and the bad taste from the DU failures becomes irrelevant.

  8. All these problems are shared with the 2012-2014 Toyota RAV4 EV.

    Lots of folks on their second and third motor. Because the Mercedes B-Class ED / B250e and RAV4 EV share the same motor with a parking pawl, they have to be rebuilt one by one, causing months long back ups of replacement motors.

    1. It just dawned on me that some folks won’t know that the above cars share the same motor as the rear wheel drive Model S (except the parking pawl in the gear box).

      1. Pushmi-Pullyu says:

        As I understand it, it is same motor, period. From what you say, the gearbox is different. Let’s not confuse the two.

        1. Airton Azevedo says:

          No Tony is saying just the parking pawl was added to the same identical Motor/gearbox (same bearings and gears) my Rav4 EV is sounding identical to the M-S in the video, time for motor replacement # 2. I like to drive a silent EV.

  9. Pushmi-Pullyu says:

    I for one would like to know what the actual failure rate is. Unfortunately there’s no way to know. Even if we had statistics on what percentage of Model S’s have had the drive unit replaced — which we don’t — that wouldn’t help much. The number of units replaced, from what I’ve read, exceeds the number of actual failures by many, many times.

    What’s going on here is that the Tesla Model S is a remarkably quiet car in operation. When a Model S is taken in for service, the Tesla techs check the car over thoroughly, looking for even potential problems, not just real problems or what the customer complained about. Tesla will swap out the drive unit if there is any sort of noise from the drivetrain, even if it’s a very minor noise which isn’t noticeable to the driver.

    Unfortunately, it looks like we’re gonna have to wait until the oldest Model S’s are out of warranty before we get any real statistics on this. We can be sure that once it’s out of warranty, Tesla will no longer be replacing drive units just because the tech hears a minor noise that doesn’t bother the driver!

  10. McKemie says:

    I just had my “drive train” replaced at about 65k miles. I would describe the noise as a “whine”. Because of publicity, I was sensitive to it but, in the absence of the warranty, it’s something I would have likely ignored for quite a while. I wish I knew about the “final” failure mode; when it stops going. In retrospect, I wish I had waited to get it repaired. To get closer to the end of the warranty.

  11. Mark says:

    I don’t think the dual motor cars are having this issue.

  12. Trex-7 says:

    It’s an American made car so one shouldn’t buy it for reliability. Tesla is just following the rest of the domestic brands. Engine, transmission, ECU replacements, and squeaks and rattles are the norm for the big three. I love Tesla and own stock, but I don’t expect them to compete with reliability in the global market. Buy a Lexus if you want a trouble free car for 200,000 MI and beyond.

    1. Foo says:

      I have yet to see a Tesla “broken down” on the side of the road.

  13. Bill Howland says:

    Well, there are EV’s that are reliable.

    From what I have seen, the VOLT, ELR, SPARKEV, and possibly also the I3 have ten of thousands (In the case of the VOLT – hundreds of thousands) of trouble free miles.

    Manufacturers other than GM and BMW should try to emulate their reliability.