How much abuse can the M3Ps drive unit take?

[Ej1749]

Apologies, if this is in the wrong section.

I have a 2020 M3P with about 35K miles on it. I drive it hard a lot. Each journey usually requires a few full launches and occasionally track use.

With an ICE car the diffs sometimes fail, not all the time but occasionally. I was wondering if anyone has any idea how many launches etc the M3P can take. As, of course, the initial torque is on a different level to 99% of ICE cars and I am worried that I am going to have the equivalent of a diff failing if I don't respect the car. I'm not too clued up as to whether there is a diff or power converter or drive unit thingy. I ask this, as my warranty runs out in December and don't want a large bill, as I will be getting a model S Plaid if it ever gets released in England and apparently it could be arriving in the UK a few months after my warranty runs out. My luck would suggest both the front and rear motors going bang a month after my warranty runs out.

Sorry for the silly question, I just wondered if the M3P is as bullet proof as it has been since the day I got it or whether I should take it more easy and lauch less... maybe only when I when I want to embarrass someone at the lights.

 

[LoL-Gas]

Nothing is guaranteed to work forever. And common sense would point to the harder you push something the more likely it is to fail.

That being said, I’d say enjoy the car to its full potential or however you want to use the car. I drove the piss out of my performance and never any drive unit issues. You paid for it so you might as well use it.

 

[DayTrippin]

Keep in mind what Tesla says about the usage and the warranty. Read this section of the owner's manual. Keep min mind all the data Tesla has access to in your car.

"The vehicle warranty does not cover damage caused by excessive overuse of vehicle components. It also does not cover racing, autocross, or driving in competition."

Model 3 Owner's Manual | Tesla

Understand how to use Track mode to optimize performance when driving on a closed circuit race track.

www.tesla.com

 

[buckets0fun]

Best bet is to have the fluids changed at Tesla on your dime, before warranty runs out. Unless you're noticing odd behaviour?

Otherwise, the oil pump would be the next guess for a wear item in high stress environment. Not a difficult or expensive repair. Part ~ 135$, can be done easily via Tesla Model 3 - Oil Change

 

[tm1v2]

My impression - just an impression - is the drivetrain on these cars is very stout. There's a good number of people on these forums who regularly launch their cars, go to drag strips, track days, etc. Most don't seem to run into drivetrain failures. The motors and battery can certainly overheat, but the car seems to be good about reducing power output to protect itself from heat induced damage.

Of course anything can fail and beating on it should induce wear failures sooner, on average, but I wouldn't worry much about it with your usage.

There are occasional drive unit failures reported here, but they don't seem correlated with how hard the car was driven, and if anything I think they tend to be at low mileage while still easily under warranty (lookup "infant mortality" in manufacturing). For the volume of Model 3's out there these days, the rate of drivetrain failures seems pretty low as best I can tell. I think the odds of both drive units failing on you are exceedingly low. Anything can happen though, make sure you have a plan that avoids destroying your life if you end up very unlucky in this regard!

However if money is tight and you want to minimize risk of failures, going easy on your car seems like a wise choice no matter what car you're driving!

You could also look into 3rd party extended warranties, I believe there are some available that include drive unit coverage. There are a lot of strong opinions of the value of such things and I'm not trying to say you should or shouldn't get one, but if the known cost of one is a lot easier for you to budget for than the potentially greater cost of failures which would be covered, maybe an extended warranty would be worthwhile for you.

Lastly, from what I've seen certain suspension bushings and bearings on this car are prone to failure, and in some cases they are correlated with how hard the car is driven. I'm not sure how much launches play into it though, vs more racetrack-style driving (repeated hard cornering).

 

[Lindenwood]

The thing is, you can’t really “launch” these with anywhere near the abuse as dumping a clutch, and they actually launch pretty soft despite the available wheel torque (1.7-1.8 60ft times are quite soft launches).

That said, heat is pretty much what kills anything—usually because heat reduces lubricity. For this reason, with consistent track use I would probably change the motor oil periodically. I am at 23k miles with 7 event days, and maybe this fall or next spring (30k miles or so) intend to get the MPP rear drive unit cooler and obviously change the motor oil (including the front) at that time. If I stick with it, I expect I’ll probably change the oils every 15-20k.

 

[gearchruncher]

That said, heat is pretty much what kills anything—usually because heat reduces lubricity. For this reason, with consistent track use I would probably change the motor oil periodically. I am at 23k miles with 7 event days, and maybe this fall or next spring (30k miles or so) intend to get the MPP rear drive unit cooler

It's simple to log motor oil temps in these cars. What oil temps are you running that makes you worried you're cooking the oil?

 

[Lindenwood]

It's simple to log motor oil temps in these cars. What oil temps are you running that makes you worried you're cooking the oil?

I certainly wouldn’t say “cooking,” and this generic chart probably doesn’t quite represent the heat tolerance of modern synthetics. Still, with our 110-115C sustained stator temps, consistent track use could degrade fluid life below the [hundreds of thousand of miles] that we would otherwise expect from a new, casually-driven drive unit.

 

[gearchruncher]

The thing is, shear stress is the more common reason for permanent viscosity ("lubricity"?) loss. Sure, viscosity changes as you heat oil, but that's temporary. Replacing the oil doesn't change that unless it's also been sheared to a lower viscocity.

Shear stress doesn't primarily come from temperature. It comes from the actual pressure between gear teeth and bearings and such that literally tear the polymer chains.

Shear Stability and Viscosity Loss

Shear stability is an important aspect of lubrication. Three of the common instruments used to permanently shear-degrade lubricants are the Kurt Orbahn or Bosch Injector, Sonic Shear, and KRL (tapered roller bearing).

www.savantlab.com

It's likely that the primary wear on a car is the total amount of time you spend at high torque. Peak torque is at lower RPM, and you can do a lot of peak torque time on the normal road if you use the go pedal like you paid for it.

You want to keep oil temps down because at high oil temps, the viscosity gets so low you are doing actual damage to the transmission in that instant. But that's very different from the fluid being permanently damaged by those temps. I can't imagine a Tesla gearbox getting that hot and otherwise surviving.

 

[Lindenwood]

The thing is, shear stress is the more common reason for permanent viscosity ("lubricity"?) loss. Sure, viscosity changes as you heat oil, but that's temporary. Replacing the oil doesn't change that unless it's also been sheared to a lower viscocity.

Shear stress doesn't primarily come from temperature. It comes from the actual pressure between gear teeth and bearings and such that literally tear the polymer chains.

Shear Stability and Viscosity Loss

Shear stability is an important aspect of lubrication. Three of the common instruments used to permanently shear-degrade lubricants are the Kurt Orbahn or Bosch Injector, Sonic Shear, and KRL (tapered roller bearing).

www.savantlab.com

It's likely that the primary wear on a car is the total amount of time you spend at high torque. Peak torque is at lower RPM, and you can do a lot of peak torque time on the normal road if you use the go pedal like you paid for it.

You want to keep oil temps down because at high oil temps, the viscosity gets so low you are doing actual damage to the transmission in that instant. But that's very different from the fluid being permanently damaged by those temps. I can't imagine a Tesla gearbox getting that hot and otherwise surviving.

I am indeed referring to lubricity, which is a general characteristic of a fluid’s ability to resist wear between two solid objects, and which itself is not inherently dependent on viscosity. Viscosity can remain relatively unchanged, but if heat has broken down some fraction of the lubricating molecules of a fluid, then overall lubricity would be reduced. Heat can and does reduce lubricity agnostic of shear stresses.

But, maybe 115C / 240F for minutes at a time isn’t enough to significantly degrade the fluid.

 

[buckets0fun]

I am indeed referring to lubricity, which is a general characteristic of a fluid’s ability to resist wear between two solid objects, and which itself is not inherently dependent on viscosity. Viscosity can remain relatively unchanged, but if heat has broken down some fraction of the lubricating molecules of a fluid, then overall lubricity would be reduced. Heat can and does reduce lubricity agnostic of shear stresses.

But, maybe 115C / 240F for minutes at a time isn’t enough to significantly degrade the fluid.

Having replaced an FDU, and rdu oil pump failing on same event, after around 40k miles of abuse, the DUs have now been placed on a 30k mile or 10hrs lapping fluid change interval.

The fluid is cheap, filling pump and special tool was cheap, spare du pumps are cheap, (in a pinch) oil filters are fk8 CTR. FDU OOW replacement cost is just shy of 5k$, not cheap.

 

[gearchruncher]

I am indeed referring to lubricity, which is a general characteristic of a fluid’s ability to resist wear between two solid objects, and which itself is not inherently dependent on viscosity. Viscosity can remain relatively unchanged, but if heat has broken down some fraction of the lubricating molecules of a fluid, then overall lubricity would be reduced. Heat can and does reduce lubricity agnostic of shear stresses.

You are claiming that in the same fluid, lubricity and viscosity are independent? And that there are "lubricating" molecules that are independent of the viscosity molecules? And that the lubricity molecules can be broken down without the viscosity molecules being broken down?

Would love to read more on this if you have a source. My understanding is that lubricity is something used to compare two different fluids. But once you have chosen a specific fluid, viscosity is a much more relevant measure. Here we're talking about a given fluid changing it's lubricity but not viscosity, PERMANENTLY due to heat, and restoring that by replacing that fluid.

What units is lubricity in and how is it tested independent of viscosity? Where can I find the lubricity of a given ATF fluid? Do you search for fluids with a specific range of lubricity when picking a fluid like you do viscosity?

Having replaced an FDU, and rdu oil pump failing on same event, after around 40k miles of abuse, the DUs have now been placed on a 30k mile or 10hrs lapping fluid change interval.

What failed on your DU? How did you guess that 10 hours was about the same as 30K miles?
It might be more interesting to do it via kWh consumed. That's representative of energy put into the gearbox. Lots of cars do this to estimate oil change intervals- they're actually basing it on fuel consumption.
30K miles at 350wh/mi is 10MWh of energy. Which to use in 10 hours would require an average output of 1MW (1,300 HP).

 

[Lindenwood]

You are claiming that in the same fluid, lubricity and viscosity are independent? And that there are "lubricating" molecules that are independent of the viscosity molecules? And that the lubricity molecules can be broken down without the viscosity molecules being broken down?

Would love to read more on this if you have a source. My understanding is that lubricity is something used to compare two different fluids. But once you have chosen a specific fluid, viscosity is a much more relevant measure. Here we're talking about a given fluid changing it's lubricity but not viscosity, PERMANENTLY due to heat, and restoring that by replacing that fluid.

What units is lubricity in and how is it tested independent of viscosity? Where can I find the lubricity of a given ATF fluid? Do you search for fluids with a specific range of lubricity when picking a fluid like you do viscosity?


What failed on your DU? How did you guess that 10 hours was about the same as 30K miles?
It might be more interesting to do it via kWh consumed. That's representative of energy put into the gearbox. Lots of cars do this to estimate oil change intervals- they're actually basing it on fuel consumption.
30K miles at 350wh/mi is 10MWh of energy. Which to use in 10 hours would require an average output of 1MW (1,300 HP).

I’m certain you can fathom how pancake syrup isn’t as good a lubricant as transmission fluid. Or that 10w-30 from the 1970s probably can’t protect interfacing metal parts from wear as well as a modern synthetic 10w-30.

Yes, two fluids—let’s even call them both lubricating oils—of the same viscosity can absolutely have different lubricity. Specifically, they could can easily have different ratios of advanced polymers and other additives that affect—you guessed it—relative lubricity under the same conditions. More pointedly, those additives or even the base fluid can and do break down over time—more rapidly as heat and/or shear stress increase. As I mentioned, I don’t have any papers to cite specific degradation rates for our transmission fluids, but I would be incredibly surprised if that rate is zero. And yes, I am unequivocally stating that you cannot simply use viscosity of a lubricant to affirm it will provide the desired lubrication.

Finally, you are again missing the heat component if you are saying 350wh/mi for 30k miles equals the same stress as 1MW for 10 hours. Even a more feasible 150kW for 67 hours would be far more stressful on our systems than 30k highway miles. Of note, for gas cars, most of their manuals state that engine oils should be changed more frequently under higher-heat operations, even if the basic onboard estimators don’t account for it.

Googling Lubricity should take you down a fun rabbit hole!

 

[gearchruncher]

I’m certain you can fathom how pancake syrup isn’t as good a lubricant as transmission fluid. Or that 10w-30 from the 1970s probably can’t protect interfacing metal parts from wear as well as a modern synthetic 10w-30.

I'm pretty sure you didn't read what I wrote in any detail. Because I said this:

My understanding is that lubricity is something used to compare two different fluids. But once you have chosen a specific fluid, viscosity is a much more relevant measure. Here we're talking about a given fluid changing it's lubricity but not viscosity, PERMANENTLY due to heat, and restoring that by replacing that fluid.

The thing is, what you said before is "heat is pretty much what kills anything—usually because heat reduces lubricity". Heat does not change one fluid into another fluid. We're not talking about comparing two fluids. We're talking about starting with one fluid, exposing it to use, and then finding that it has degraded in properties enough that it needs to be replaced. In a way, that is two fluids. But it's not completely independent, as all of that oil was exposed to the same degrading environment, not just the "lubricity molecules." And history has found the permanent viscosity change is much more important than some change to the secondary lubricity property.

Googling Lubricity should take you down a fun rabbit hole!

Ahh, the old dO YoUR REseaRCH chestnut. Especially from someone saying "As I mentioned, I don’t have any papers to cite specific degradation rates for our transmission fluids, but I would be incredibly surprised if that rate is zero."

I did do my research before I began this discussion, because I was surprised by your statement and wanted to learn more. I could find very little about lubricity in a GIVEN oil that was not dominated by viscosity. I even posted one of those links above. But here, to get us started, are some elements from the Wikipedia lubricity article:

The lubricity of a substance is not a material property, and cannot be measured directly. Tests are performed to quantify a lubricant's performance for a specific system.

For two fluids with the same viscosity, the one that results in a smaller wear scar is considered to have higher lubricity.

So let me ask again: How does heat degrade lubricity in ATF without degrading viscosity, given lubricity is completely irrelevant if viscosity has changed? How are you so sure that in the Tesla Drive Units that the degradation we are worried about is a reduction in lubricity due to heat, not viscosity changes due to shear down? Why is it that when I google "lubricity change shear down" all I find is hundreds of articles talking about viscosity?

 

[Lindenwood]

I'm pretty sure you didn't read what I wrote in any detail. Because I said this:


The thing is, what you said before is "heat is pretty much what kills anything—usually because heat reduces lubricity". Heat does not change one fluid into another fluid. We're not talking about comparing two fluids. We're talking about starting with one fluid, exposing it to use, and then finding that it has degraded in properties enough that it needs to be replaced. In a way, that is two fluids. But it's not completely independent, as all of that oil was exposed to the same degrading environment, not just the "lubricity molecules." And history has found the permanent viscosity change is much more important than some change to the secondary lubricity property.


Ahh, the old dO YoUR REseaRCH chestnut. Especially from someone saying "As I mentioned, I don’t have any papers to cite specific degradation rates for our transmission fluids, but I would be incredibly surprised if that rate is zero."

I did do my research before I began this discussion, because I was surprised by your statement and wanted to learn more. I could find very little about lubricity in a GIVEN oil that was not dominated by viscosity. I even posted one of those links above. But here, to get us started, are some elements from the Wikipedia lubricity article:




So let me ask again: How does heat degrade lubricity in ATF without degrading viscosity, given lubricity is completely irrelevant if viscosity has changed? How are you so sure that in the Tesla Drive Units that the degradation we are worried about is a reduction in lubricity due to heat, not viscosity changes due to shear down? Why is it that when I google "lubricity change shear down" all I find is hundreds of articles talking about viscosity?

So… bottom line… neither of us know whether it’s worth changing the fluid?

 

[Ej1749]

Thanks for all of the advice and debates. I appreciate the help.

 

[golfcart]

How long are the CV axles on the model 3s lasting? I am kind of amazed given the amount of torque these cars make and how hard a lot of us drive them that I haven't heard much about them getting shredded. That always seemed to be a common point of failure with my modified "sport compacts"... maybe these are just engineered better.

 

[Gasaraki]

I'm sure Unplugged Performance can answer that question since they used a Model 3 for their pike's peak run. They know how robust the drivetrain is.

 

[Lindenwood]

How long are the CV axles on the model 3s lasting? I am kind of amazed given the amount of torque these cars make and how hard a lot of us drive them that I haven't heard much about them getting shredded. That always seemed to be a common point of failure with my modified "sport compacts"... maybe these are just engineered better.

He thing is, torque can’t actually ramp up that quickly on these vehicles (hence the 1.7-1.8 60ft times, rather than the 1.4s-1.5s you’d expect with this much power). Just as importantly, the drive systems are incredibly good at cutting power at the tiniest indication of wheel slip, wheel hop, or even just hitting a bump under load. Shock loads break hard parts like CVS and axles, and there are almost none coming out of our drive units!

 

[gearchruncher]

The Tesla drivetrain also has way less inertia than an ICE vehicle. Upstream from the half shafts is only a diff and a rotor.