Front Drive Unit Failure

Front Drive Unit Failure

Just picked up my dual motor M3 and had a front drive unit failure within the 1st 50 miles. Now it has been sitting at the service center for over a week with the hope of getting a replacement part (a new front drive unit) in another week. I have really enjoyed driving the car for the brief time I had it. The VW loaner they gave me most certainly pales in comparsion. While the technology, driveablilty and responsiveness of this car is truly in an elite class of its own, the customer service and support has a long way to go to be in line with other premium auto makers. They have been a bit non-existent through this experience and would appear to be oversaturated and unable to deal with the volume of demand they are experiencing lately.

Magic 8 Ball | October 6, 2018

Bummer, you got a rare case of infant mortality and a major component like that would not be a shelf stock item anywhere.

jordanrichard | October 6, 2018

Is the car undriveable? Seems to me that your car should still be able to be driven albeit as a RWD.

srud0927 | October 6, 2018

The car was drivable in sort of a limp mode, roadside assistance recommended it be taken directly to a service center.

BostonPilot | October 7, 2018

@ jordanrichard I was wondering the same thing. Tesla made some statement (maybe it was Elon?) about the reliability in that if one motor failed you could still drive on the other. Why should it be in a limp mode if it still has one functioning electric motor?

GaryTheBadger | October 7, 2018

It's still on the Tesla site...see the last sentence: "Tesla All-Wheel Drive has two independent motors. Unlike traditional all-wheel drive systems, these two motors digitally control torque to the front and rear wheels—for far better handling and traction control. Your car can drive on either motor, so you never need to worry about getting stuck on the road. If one motor stops working, you can safely continue to your destination with the second."

ebmcs03 | October 7, 2018

You can safely continue to your destination. (In limp mode)

Doesn’t mean you can still drive it on a regular basis.

gmr6415 | October 7, 2018

"If one motor stops working, you can safely continue to your destination with the second..."

That's a pretty broad statement. Stops working could simply be loss of current or something of electrical nature. My understanding there is a gear box, and if something in the gear box failed I doubt you could still drive it. If a bearing in one of the motors failed the same. There is also an open differential. If one of the gears failed you wouldn't be able to drive it either.

There is a lot more in the either drive unit than just an electric motor.

Magic 8 Ball | October 7, 2018

@gmr6415 The statement is clear and true. Someone has already claimed to have had a motor failure and got to their destination. You are choosing to make a broad interpretation of the statement where I take it for what it says and have no reason to believe "motor" means drivetrain.

BostonPilot | October 7, 2018

@ GaryTheBadger - Thanks for finding that... Yeah, I would certainly interpret "If one motor stops working, you can safely continue to your destination with the second." to not mean a limp mode.

@ srud0927 - what was the actual indication that you had a problem? Was it a message, and if so what did it say?

Mediumed | October 7, 2018

I love Tesla and I love my Model 3 but sometimes you need a law degree to decipher the statements that are made by the company.

srud0927 | October 11, 2018

@ BostonPilot - the error message was "Front Motor Disabled" with some additional comments about the vehicle will continue to operate with reduced power. The performance loss was significant and very apparent, especially when merging on to the freeway.

Magic 8 Ball | October 11, 2018

I would expect that having only one, out of two, motors working that performance loss was significant. So you were actually able to drive at freeway speed with the one motor?

jordanrichard | October 11, 2018

Gmr6415, The “gear box” is what Tesla calls a gear reduction box. It is like a differential. There is no gear box and then an “open differential”. The drive unit is made up of 3 components. An inverter (no moving parts), the gear reduction box, and the motor, which has 1 moving part and that is the rotor. The rotor is supported by 2 bearings. These are not bearings like the ones found on the crank shaft. These are like ceramic ball bearing, bearings.

The only way a motor will fail is if the bearings physically come apart. For the gear reduction box to fail and gear would have to come apart. How often do you ever hear about someone rear differential failing in an ICE car?

Frank99 | October 11, 2018

>>> The only way a motor will fail is if the bearings physically come apart.
That's a somewhat limited view of the world. The motor will fail if one of the windings breaks, or if the electrical connection to the inverter breaks, or if one or more of the IGBT's in the inverter breaks, or ....

The only thing that would prevent you from driving the car would be a catastrophic mechanical failure like the bearings coming apart. But there are lots of failures that would prevent the motor from being used, but wouldn't impact the ability to drive the car (though you'd be limited to RWD power).

gmr6415 | October 11, 2018

@jordanrichard, As with any vehicle the drive unit of a Tesla has to have a differential in order for cornering. The inner tires have to slow down and the outer tires speed up when turning and driving around curves. The Tesla drive unit is comprised of the electric motor, the inverter, the reduction gear box and a differential. The open differential of the Tesla has 4 spider gears or pinion gears just like any automotive drive unit.

And who said the bearings are like those on a crankshaft. If you'v ever had an electric motor apart almost all of them have ball bearings. Conventional starter motors tend to have bushings because they turn at relatively slow RPM and only they only turn when starting an ICE.

I suggest you watch this video starting at minute 6.

As some who was a mechanic for over 2 decades I can tell you differential failures in standard ICE cars are as common as transmission failures or engine failures. Anything in the drive line can end up being the weakest point and fail under stress. Do you have any idea how many people blow rear ends racing their cars, spinning wheels around corners, etc? It's more common than you think.

gmr6415 | October 11, 2018

@jordanrichard, Here is an add selling a roadster/model S differential.

If you followed the trials and errors of the early roadsters the biggest failures were that the limited slip differentials couldn't handle the torque and often broke, which is why Tesla went to an open differential.

Standroid | October 11, 2018

I wonder if there has been an evolution in the understanding within Tesla engineering of the wisdom of moving an unpowered drivetrain. On the one hand there is the statement quoted above that one motor can take on the whole job in the event of a single motor failure. On the other hand there is the flat prohibition against flat towing with wheels on the road. It would seem like the single motor case is the same as flat towing to the other motor. In any event I hope the evolution continues - at least in the direction of greater clarity for owners.

srud0927 | October 11, 2018

@ Magic 8 Ball - yes, I was able to do every bit of 75-80 MPH on just the rear motor, however it did take much longer to get there.

Magic 8 Ball | October 11, 2018

Thanks for the update. "Limping" is not as bad as I envisioned. ; )

lbowroom | October 11, 2018

80mph limp mode. What was your planned velocity?

Fuzzball | October 11, 2018

srud0927 - I would call the service center and immediately ask for a tesla as a loaner. you dont want to be driving that crap.
My story is that my frunk got stuck. I took it to service and they said they need 3 days as they are backed up. They gave me an Audi Q5 as loaner since they were backed up on loaners too. I got a call 3rd day that car will be ready after cleanup in an hour. Half an hour later i was told they damaged the car (banged the rear quarter panel) so they have to take care to body shop. I immediately demanded a tesla as a loaner and they delivered it to my home and took away the shitty Q5. However, purpose of long story is to tell you its been OVER A MONTH and they are still awaiting the rear panel. And i anticipated that - why wouldn't they want to put the part in a new car with new sales while in advise, get a tesla as a loaner, who know how long you are out of your vehicle....

ODWms | October 12, 2018

“...and took away the shitty Q5.”

Gotta love it!!!!

Coastal Cruiser. | October 12, 2018

sromoda: LOL.

Standroid, good points there. I've always wondered why you had to flat tow the cars. Perhaps it is due to a lack of a "true" neutral separating the gearbox from he motor. Question mark.

But if it turns out to be true that it is indeed safe to drive to your "destination" on one motor, it would not be surprising to see Tesla implement a software feature with the ability to switch to a single drive algorithm, so that one would not have to limp to one's destination. (just joshin' you srud0927). :>

johnse | October 12, 2018

I has a Jeep Grand Wagoneer. It would occasionally have a “clunk” sound in the rear end when I accelerated from a stop. We were living in Reno and visiting then-wife’s family in Santa Cruz. Mechanic friend of the family looked at it. Thought the spider gears were a little loose in the rear differential and might slip occasionally. Said if it finally failed, I could at least keep going by engaging 4wd, being effectively front wheel drive.

So that (we thought) happened. Car wouldn’t move in RWD. Drive shaft was spinning, but wheels didn’t turn. We needed to get home and I planned to get it fixed in Reno....

Middle of the night on I-80 about halfway to Donner Summit, the left rear wheel falls off. I see a fan of sparks covering the road behind me as the lower 1/2 inch of the brake backing plate grinds off on the road. Front wheel drive allowed me to maintain control and pull off the road.

Turns out the “key” locking the rear wheel hub to the axle had sheared. The clunk was the axle spinning once and then the key catching it again. It finally wore down so it didn’t catch any more and so the hub was freewheeling on the axle until finally the axle bolt came off.

Not quite a differential failure, but likely even less common. Always good to get definitive fault diagnosis when possible :)

johnse | October 12, 2018

*had, not has... this was in the ‘80s.

FifthOnLeft | October 12, 2018

I took delivery of a P3D+ about 2 weeks ago, and had the same "Front motor disabled / Power reduced" message after a 20-mile "test drive" that ended with an "emergency braking" test from 40 mph. The message came on right after the braking. The loss of power was immediately noticeable as only the rear motor was working. It was not in a true "limp mode" and felt like the RWD.

Mysteriously the message did not come up at the next start. The car seems to be back to full power now but I haven't driven much to confirm (a quick 0-60 test showed low 4s from a stop watch). I will be conducting more speed and braking tests this weekend and will contact service if that issue shows up again.

BTW, the OBM paint with Ceramic Coating looks great especially in the sun. Great car overall, but may need beefier rear tires for spirited driving in the back roads.

coselectric | October 13, 2018

For comparative purposes, my Subaru has been "limping" its way up to 80 mph on the highway since, well, it popped out of the factory.

dvernier | January 19, 2020

My newish P100DL is in Tesla service, where it's been for the last 10 days. We were at the end of a 1500 mile trip going 70 MPH when the "Front Motor Disabled. Power Reduced" message popped up. There was also a "cute" image of a smiling snail next to the message. There is about 10,000 miles on the car. So, for the next 30 miles to our final destination, the car used only the rear motor but kept up highway speeds. It did "limp" up my driveway that has a slight upward incline. I asked the service manager if front motor failure is a common problem, and she responded, "I don't know how common, it is, but I have seen this before." So I would be interested in hearing from others who have experienced this failure. How common is the message "Front Motor Disabled..."?

BritMob | January 20, 2020

I got it at 47 miles, MS AWD LR, exact message above. I limped almost home until it failed in the middle of an intersection. 3 weeks at the local Tesla shop, and apparently they had to call the engineering team. In the end, they gave me a new motor and it's been perfect ever since (over 20k miles now). I would assume they'll rip your current motor out and give you a new one.

BritMob | January 20, 2020

edit: M3, not MS