UPDATE: Majority of Early Tesla Model S Cars Could Require Drivetrain Replacement After 60,000 Miles, Data Suggests

December 10, 2015 Update: We’ve been informed by PIA that the study data from which this report is collated recorded actual drivetrain replacements among Model S cars rather than drivetrain failures. Since Tesla Motors was (for some time) replacing entire drivetrains of customers’ cars when receiving complaints about excessive noise or other faults, it is perhaps fairer to treat this study as one in which drivetrain replacements are tracked rather than total failures — although we will let the reader draw their own conclusions.

It’s no secret that when it comes to happy owners, the Tesla Model S electric car has the highest customer satisfaction of any car on the road today.

Even the venerable Consumer Reports, which recently removed its coveted red-tick recommendation due to a higher-than-average reported fault rate in its annual automotive reliability study, conceded that while Tesla cars appear to require more visits to the shop than some other brands, 92 percent of all Tesla owners would buy another car.

How reliable is the drivetrain on early Tesla Model S electric cars?

Even when their cars have to visit the shop, and owners find themselves with a far longer wait time for the repair than they once did, Tesla still seems to keep its customers happy.

That could soon change however, with news of a statistical analysis that suggests more than two-thirds of all early production Model S electric cars will suffer a drivetrain failure may require drivetrain replacement after covering just 60,000 miles. If true, it could put extra strain on Tesla’s already hard-worked service centres and perhaps even change the brand’s reputation among its owners.

We're not mathematicians, but this analysis suggests two-thirds of 2012 and 2013 Model S cars will suffer drivetrain failures after 60k miles.

We’re not mathematicians, but this analysis suggests two-thirds of 2012 and 2013 Model S cars will suffer drivetrain failures after 60k miles.

As our friends over at GreenCarReports explain, it has just completed an extensive analysis of data provided by 370 Tesla Model S owners via a Plug In America on-line survey form. The form, initially set up to allow Tesla Model S owners to share their experience with battery pack capacity and how it changes over time and distance driven, also asked owners to report their charging habits, driving habits, odometer reading and any replacements undertaken under warranty of the car’s battery pack, on-board chargers or drive unit.

The data from those cars as collated in October can be seen on the Plug-in America website, and seems to represent a wide enough range of  different Model S variants from 2012 thru 2014 model year cars located across the U.S., Canada and Europe. Since Plug In America made the raw data available for further analysis — and the data set included questions on drivetrain replacement — GreenCarReports’ Matthew Klippenstein (aided by a friendly reliability engineer) used the same data set to carry out a mathematical analysis on drivetrain failure rates.

Cleaning the data up to account for any errors in survey completion, a process which Klippenstein says he corrected errors favorably in Tesla’s favor, he then proceeded to execute a Weibull statistical analysis of the data in order to project probable drivetrain failure rates at given ages and mileages.

The result? Of those 2012-2013 Tesla Model S electric cars surveyed using the freely-available Weibull ++ software from ReliaSoft, Klippenstein concluded that more than two-thirds of the early 2012-2013 Tesla Model S cars made will likely suffer a drivetrain failure get a replacement drivetrain after 60,000 miles of use.

Tesla has said multiple times that the design which led to drivetrain failures has now been changed.

Tesla has said multiple times that the design which led to drivetrain failures has now been changed.

Using the same procedure, he notes that the Tesla Model S battery pack and onboard charger have a much longer life, with the on board charger for example likely to have a characteristic life of more than one million miles.

As Klippenstein notes, the data itself contained within the Plug In America survey is too small to be of use when it comes to later model-year Tesla cars since only a handful of 2014 model year cars were included in the survey. As a consequence, he negated to publish a statistical analysis of such a small data set.

At this point, we feel it’s important to note that the statistical analysis was carried out independently to Plug In America and as of the time of writing have yet to make an official statement on the analysis.

In response to questions from GreenCarReports over the analysis, Tesla Motors declined to answer specific questions about its own reliability data, replacement drivetrains carried out to date, or reliability of future drivetrains on later model year cars.

Instead, it issued the following statement, which we’re quoting from GCR.

Close communication with our customers enables Tesla to receive input, proactively address issues, and quickly fix problems. Over-the-air software updates allow Tesla to diagnose and fix most bugs without the need to come in for service. In instances when hardware needs to be fixed, we strive to make it painless.

I would point you to Elon’s previous comments, here and here, as well as whatConsumer Reports recently [wrote]:

Despite the problems, our data show that Tesla owner satisfaction is still very high: Ninety-seven percent of owners said they would definitely buy their car again. It appears that Tesla has been responsive to replacing faulty motors, differentials, brakes, and infotainment systems, all with a minimum of fuss to owners.

And Tesla’s attention to customer service has been effective. Almost every survey respondent made note of Tesla’s rapid response and repair time, despite the lack of a traditional dealer service network. For its early adopters, Tesla has made a practice of over delivering on service problems under the factory warranty…

Do you own a 2012-2013 Tesla Model S? Has your car suffered a drivetrain failure? Or are you an owner who has found the drivetrain to be reliable thus far?

What do you make of the analysis? And does it change your view of Tesla reliability?

Leave your thoughts in the Comments below.

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