Milling Through the Mire: Tesla Model S Drive Unit Woes

We may have mentioned that the road to EV nirvana worldwide might be a tad longer than the press and His Eminence Herr Musk might lead you to believe. Stay with EVTV. We will get you there. We've seen this all before on the Internet rodeo in a past life. And trust me, it's all going to happen - just not as quickly as you might want.

Electric Vehicles have had a mixed recent history actually. EVTV has kind of carved a niche out by doing strafing runs on bankruptcy auctions of the limp, the lame, and the dead strewn across the prairie of the Electric Vehicle frontier. We actually compiled a list of all the electric vehicle startups of the past five years who haven't made the trip and we keep adding to it. It's hard to remember them all.

The one bright spot in the firmament has been Elon Musk and Tesla Motors. We've profited personally and handsomely on just daytrading the stock of Tesla - sufficiently so to finance a P85 model sufficiently loaded to total $107,000 ducats. Many of our viewers have done likewise, and indeed some have also bought a Model S. We are unabashadly Tesla Fanboyz. But we do keep our eyes wide open and take our duties regarding keeping our viewers informed quite at the top of the priority heap. And the rule is if you have a problem sufficiently serious that it gets its own name, you indeed have a problem. In this case, it is the Milling Noise problem.

And not everything always goes 100% smoothly.

Some Tesla owners are experiencing difficulties. This one stepped on the wrong pedal at the wrong time - at the Freemont service center as it turns out. It's a sign of the times.

We had an interesting conversation with a near fanatic Tesla Model S owner. Joe Robe lives in Florida but has already attended several Model S gatherings on the WEST coast. He drives his Model S cross country and in just a few months of ownership has driven over 40,000 miles. He's also on his THIRD drive train and second battery pack.

Much is made of Tesla's Supercharger network and it is indeed a plus. But Joe needed to stop in Cape Girardeau on his way to St. Louis from Nashville, enroute to a Model S gathering in Monterrey. He contacted us by e-mail and I responded that we did indeed have a real Tesla charging station and indeed three of them here in Cape Girardeau and he would be welcome to stop and charge.

He picked a kind of an inconvenient time to do that, right during dinner celebrating a friends birthday at 9:15 on a Saturday evening. But we went down to the shop and let him pull his white Model S into the shop and plug it into our Tesla charger, which is a well fed model that can do full current. We gave him the Azure Dynamics eTransit Connect to take to the hotel and he found it most delightful to drive.

We met the next morning for a tour of the shop and found that Joe was a software engineer and a bit of a teutonic Cherman perfectionist. He told a tale that is becoming quite familiar - inoperative charging stations across the land. He was delayed in Nashville at a Nissan dealer's who's charge station would run for just a few minutes, overheat, and shut down.

But Joe is a resourceful guy. He cleaned out the intake grill on the charger and got it up and running. Indeed he had to fix several charge stations on this trip from Tampa.

He also showed us a Chademo to Tesla charge adapter that is supposed to be a state secret at Tesla but is available actually. It's $1000 and available "soon" but he had one.

He reports that there is nothing wrong with Chademo and he was easily able to charge his car adding 140 miles in range in a one hour charge.

But he also reports that with over 40,000 miles on his Tesla, he is on his THIRD drive train and SECOND battery pack. The battery exchange was actually, according to Joe, simply a fuse in the battery pack that had blown. But the Service Centers aren't allowed to access the inside of the battery pack. Tesla shipped an entirely new battery pack to the local service center and they swapped it out in a matter of minutes.

The drive train is slightly more ominous. Tesloids already have a name for it, the MILLING NOISE. We admitted we only had 4800 miles on our Model S and Joe assured us - you will have to replace your drive unit at 8000 or 10000 miles.

There are also reports of a "klunk" sound when going from acceleration to regeneration and back. But the majority of failures involve a grinding or "milling" noise that increases over time.

After our conversation, Brain and I looked about the Internet and Brain came up with two very interesting reports because they are so public. Motor Trend Magazine has a Tesla Model S and they report that they had to have a drive unit replaced. More ominoous, Edmunds reports they are on their FOURTH drive train. This is a bit disingenuous. They are actually on their third drive unit. One that was delivered to the Service Center was rejected for a broken electrical connector.

Rumor has it that one Service Center employee admitted they were changing 3 to 5 drive units per week.

Tesla features a 4 year, 50,000 mile warranty. For $4000 you can extend that another four years and you might want to take advantage of it. Some commercial buyers are not eligible for the warranty at all and at least one was dinged $15,000 for the drive unit replacement.

The drive unit itself is kind of an integrated unit consisting of the Tesla manufactured copper rotored AC induction motor on the left, the power electronics on the right, and a single speed gear reduction/differential unit in the center. It features a 9.73:1 gear reduction. No one appears to know where this gear drive comes from. Tesla used Borg Warner and an eGearDrive on the Roadster. From the looks of it, this Model S gearing has almost the identical cast aluminum type of case and it is entirely out of the question that Tesla is making their own gearboxes. But they are so secretive about it that there is so far no way to confirm that Borg Warner is a supplier of this unit. But to produce a gear drive unit like this in the numbers required, we would be astounded if it was any other but.

We actually sell the eGearDrive of Borg Warner quite similar to the one on the Tesla Roadster. We've kind of developed a following among Ford Dealers attempting to support the eTransit Connect as they apparently have a quite high failure rate. I would venture a guess that this is the heart of the TEsla Model S drive unit problem. The radial load on the motor just shouldn't be sufficient to point to a motor bearing, though the Model S does appear to use a very unusual open lubricated bearing. But milling noises and klunks are classic transmission type failures.

And in one sense, any wonder. Our P85 motor is capable of 600 Newton Meters (435 ft lbs) using 305 kW of power. Applied instantaneously at moving 4675 lbs of car, plus people meat, forward, the forces are very very large. More importantly, and I was quite called to task by Otmar, who is no longer discussed at EVTV, for my characterization of the very small time frame of electric motor torque application. It remains actually pretty accurate.

When you accelerate an ICE engine, there are a couple of things going on - none of it very direct. Stomp on the pedal in your brand new Vette and what you really do is open up the flow of intake air and fuel into the carburator or more likely fuel injectors. This causes the motor to increase in RPM but in a kind of logarythmic growth curve. At first quite slowly and then at an increasing rate. Along the way, if you have an automatic transmission, you have the further spoolup of the torque converter until it reaches lockup. The result is a kind of controlled application of the power ramping to maximum over the span of 500-700 msec.

To put that in perspective, the CODA UQM CAN module I'm working on would have sent 70 torque commands to the inverter in that time span. It would be of no advantage, but quite easy, to spool up an electric motor in 10 to 20 milliseconds. Worse, you could apply the entire 600 Nm with the FIRST TURN of the shaft - actually at stall.

Understand that this is entirely uncharted territory. Tool steel facing sudden shock forces actually does change its crystaline structure - I characterize this as gelatinize much to Otmar's mirth. It reforms quite quickly. But I've held the results in my hands several times. The most mystical of these was a one inch diameter shaft on a puny 30 kw MES DEA motor. We had made an adapter for their involuted spline from 4041 hardened tool steel. The shaft of this adapter was less than 3 inches long. BUt we have one with a 3/4 twist in it that I marvel at every time I pick it up. It just defies belief.

Of course, the result of an inverter mishap. And no doubt, like all inverters, the Model S has certain rampup rates, usually termed "slew rates" built into the software to ramp up the application of torque. But the Model S is striving for that 0-60 in 4.2 seconds. It weighs 4675 lbs. The resulting forces are simply non-trivial.

ICE cars often have acceleration rates that are quite similar and even higher torque values - in some cases MUCH higher. So how is this new. Again, the only difference is the slew rate or ramp rate of the application of power. NO production car on the planet has the instantaneous take off of the Model S. You can beat it in the quarter mile. But no ICE engine car would be able to even come close in the first 500 feet. It's not even theoretically possible.

So while we have heard grousing about fender bolts and some angst over steering knuckles, charging issues, and bluetooth, why hasn't this been more widely discussed in the media?

There is kind of a natural ad hoc conspiracy of silence on the topic. Tesla is as described, one of the more secretive organizations on the planet, making our CIA and NSA look like a hotbed of whistleblowers. But realistically, most Tesla owners are Tesla stockholders as well. There ARE some discussions of it in the Tesloid forums. But we found one post reprentative. One Tesloid with 87,000 miles on his allowed that he had indeed replaced the drive unit at 40,000 miles, but didn't think it significant to mention as he hadn't had a single problem since. Best car he's ever owned. Etc. etc.

The DRIVE UNIT is equivalent of the ENGINE AND TRANSMISSION AND DIFFERENTIAL on any normal production car. And it is apparently post warranty at $15,000. That kind of bears mentioning.

So beyond the stock price, this rather goes to the value of the car. If it becomes widely known that post warranty at 50,000 miles, you rather inevitably face further drive unit replacements at $15,000, we are looking at a resale value on a four year old $107,000 Model S somewhere north of about $5700. That's pretty valient depreciation.

I have mentioned a number of times that one of the herculean obstacles to electric vehicle adoption is the value proposition - how much of a premium above the cost of a similarly equipped gasoline car will electric drive command AFTER we are all acculturated to and knowledgeable about the advantages of magnetic drive.

What we've never really discussed at any length is the other end of the stick. Resale value. This actually IS the 800 lb gorilla in the room. Almost everyone is taking kind of a wait and see view of electric cars and I think it is on this issue more than "range anxiety." EVERYBODY viscerally understands the concept of batteries even if it comes "batteries included". Nissan has just attempted to address this issue by announcing a purportedly reassuring $5495 replacement cost on their batteries. They aren't actually offering it and you can't actually get it but they have actually announced it. And it is in an attempt to address the thoroughly one sided statistics on Leaf leases versus Leaf purchases. Nobody is buying. Everybody is leasing. And Nissan is dutifully reporting each lease as a sale. It is not. It is typically a two-year lease at that.

The battery is kind of a known and understood problem inherently part of electric cars. But if it became known that Tesla had a problem with essentially the entire drive train - and a $15,000 issue at that, what would THAT do to resale value? And so I sit on a $107,000 car, that if you knew the troubles its seen you wouldn't buy on a bar bet for pretzel money, should I mention it? Who wants a car where you replace the engine four times for each tire replacement?

Given Tesla's stock volatility, you might consider a few PUTS to protect your shares or maybe get out of them until this is resolved.

Interestingly, I got a call from CAMERON at the Tesla Service Center in St. Louis WHILE I was writing this. He was calling to REMIND me that my annual service inspection is due. We worked out next Tuesday as a fine day for an inspection. I really wasn't wanting to take a day right now and drive up to St. Louis for an inspection, but we have been having the steering knuckle noise so I supposed I must. I was astounded to learn they intend to come PICKUP the car at 9:00AM Tuesday, take it to St. Louis on a truck and do the inspection, then return the car THAT EVENING or perhaps the next morning. The service being offered is just unbelievable.

I did ask Cameron if they were replacing any drive units these days. He admitted they were - people were reporting a "whirring noise" as he characterized it.

This video describes a Tesla owner who's car was in the Service Center for a purported 66 days. They sued Tesla for the cost of the car plus $18k in legal fees. Tesla settled for the requested amount. But the Tesla apologists and fanboyz have attacked the lawyer as some sort of scumbag. Had we had a car in for service for 66 days, he would be a hero at my house.

So your mileage may vary. I'm astounded at how GOOD the Tesla service really is. And thoroughly alarmed that they may be facing a recall of the entire fleet for drive unit issues - a non-trivial expense.

One thing is fairly certain. They can't just keep installing new drive units in Teslas every 10,000 miles. I have to believe there is some panic in Freemont these days, trying to come up with a solution to a new drive unit that is much more durable to offer as a replacement. They have 35,000 cars out there now and how they are going to "fix" this and survive financially is a little muddy.

Worse, I don't think there is really very much "wrong" with their drive train. If it's the gearbox, about the only game left that can deal in that technology and those numbers is Getrag. And they do NOTHING quickly. My fear is they have run into a wall of hubris that cannot be re-engineered.

I am a huge advocate of electric cars. I just love them and I never get over it. I will not rest until we replace 1.5 billion gas burners with 1.5 billion battery powered cars. But there are a few myths about electric cars that in the long term are counterproductive. One is that they never need maintenance. Joe Robe AFTER noting three drive unit replacements and one battery swap, assured me with an absolutely straight face that electric cars are "maintenance free." I laughed out loud and called him on it and he very excitedly if not heatedly noted that those were all EXCEPTIONS and without these problems electric cars are maintenance free. Let me assure you Joe, they are NOT maintenance free. They are somewhat maintenance expensive actually. It is DIFFERENT from ICE cars. But it is not maintenance free.

And I fear in the case of Tesla that we have birthed a performance myth. Yes, they DO perform better than ICE cars and yes acceleration IS instantaneous. But we have 150 years of Darwinian evolution of the transmission based on a 500-700 msec ramp rate. The gearbox is what has plagued Tesla from the FIRST prototype they built, and I'm guessing it is very much the topic of conversation in Freemont right this minute. Electric vehicle performance and acceleration are not without limits. And it is my personal opinion that they have found the limit in the gearbox. The acceleration of 4675 lbs at a sufficient rate to move it to 60 miles per hour in 4.2 seconds is really not done guys. Sports cars at 3000 lbs do that with a 700 msec spoolup.

Our own Kevin Smith learned the hard way with Illuminati. He basically built an electric car in a corn field on a shoe string and had the Progressive Insurance X Prize essentially in the bag - until his transmission completely self destructed on the track. Again with a little 30kW MES DEA motor. He really DID have it won. Millions in prize money. For a guy in a barn who works at a government job. For lack of a transmission. If he does ever get over it, I won't get over it FOR him until three years AFTER he gets over it.

At this point, one thing Tesla has done right is attract a lot of very smart guys to California to work on this car. The solution to most technical problems is a function of desire, time, and money. But THIS problem could pressure the time and the money end of it. And I fear the ultimate solution is a 6 second acceleration rate - which I could live with just fine actually. I believe they will find the answer is a few lines of software code, but the answer will not be very satisfying to those who liked the performance claim on this car. It think the claim was unrealistic from the get go. Actually I did NOT find it unrealistic, I found it SURREAL. A light weight Lotus Elise? Sure. A 4275 lb sedan with seating for another 1000 lbs of people meat? Copper foil helmet award. Right out of the bag.

I'm pulling for them. But I think this particular issue is very very grave. And I don't want the Al Gajda's and Jeff Southern's and others among our viewers to get the word later rather than sooner because I just didn't want it to be so.

Our show this week is I believe the longest we've done at two hours and 48 minutes. That's the length of two feature length films. We have a new quadracopter video camera intro and lots to catch up with as we took off for the Fourth of July. I was most pleased with a 30 second suprise at the end of the show - the first vehicle moving with my CODA/UQM Powerphase 100 GEVCU module.

As my brother Thomas is marrying this week, we'll miss another show for July 18th. I'm off to Point Clear Alabama to offer a toast. I face two younger brothers in a to-the-death golf match on Friday morning when I should be filming. I haven't had a golf club in my hands for five years and they play like they don't have a job to go to. At least I won't be Elon Musk this week.