For those who want some background on this, recently there have been some minor drivetrain issues that have creeped up (see quote below from last quarter's TSLA conference call).

As a result, some potential customers were getting concerned about the reliability of Tesla's drive train especially since it's only covered under the 4 year (50k) warranty. So, Elon decided to extend the drive train coverage to 8 years, and this significantly makes the car more appealing to potential customers since they know Tesla will take care of the biggest problems (ie., the most expensive part of the car is the battery and drive train, which are now both covered for 8 years). This is a great move by Tesla and should show people how committed they are to product quality and to the ownership experience.

Below is from TSLA's Q2 quarterly conference call:
http://seekingalpha.com/article/2368515-tesla-motors-tsla-ce...

"We definitely had some quality issues in the beginning for the [indiscernible] number of cars, because we're just basically figuring out how to make the Model S. And I think we've addressed almost all of those CARB [ph] production cars, I mean not all, but the vast majority have been addressed in cars that are being produced today.

And we're also getting better at diagnosing what's wrong, because in some cases we, particularly with respect to the drive unit, we think that something is wrong with the drive unit but it's actually something wrong with another part of the car. And then we'd replace the drive unit and that wouldn't solve the problem because the drive unit was not the problem.

And we had one particular case where there was vibration, and it was due to -- it was due to the -- a cable detaching itself and touching the drive unit assembly and causing vibration to be transmitted to the body of the car. And it was somewhat pernicious because if the cable moved a little bit and so that it didn't provide a conductive path, then you wouldn't -- the vibration would go away. If you replace the drive unit, you temporarily tuck the cable back and think the problem was solved and it was -- but then the cable would vibrate itself down and transmit the energy. So I mean that, you know, the cable thing takes us like -- it's nothing to fix it. It's like, virtually, it's like a $3 cable tied to solve it.

So there's a bunch of things like that which are just [indiscernible] diagnosis of the problems that we've obviously addressed.

There are a few items that will need a fair number of drive pans [ph] will need to be serviced. It's actually related -- one particularly is related to the differential, and we need to assume [ph] the differential. It doesn't require drive unit replacement, it just requires a technician to insert a Shim [ph]. We're going to have to do that on a fair number of cars. But that's like a $0.50 Shim [ph].

So it's really -- I wouldn't assume that there's going to be some vast number of drive pans [ph] that will need to replaced, but there's several service buttons [ph] that we'll be instituting, many of which we've already have to address the issue.

And every week I have a product excellence meeting, which is to -- which is a cross-functional group, so we've got engineering, service and production, and we go about all the issues that the customer is reporting with the car, and, you know, the action items that we addressed to get car ultimately to -- photonic ideal of a perfect car, that's what we're aiming for. Because although we -- I think we've got great service, but that service is no service. That's really what we want, is a car that never needs to be serviced. And I think we're getting there quite rapidly."