Parking pawl integrity

[Pianewman]

88xxx here. QUESTION: Does anyone know how robust the parking pawl is on Tesla drivetrains?

Coming from hilly Northern VA, I learned, and convinced my wife and children, to ALWAYS use the parking brake. "Make it a habit, to protect the transmission."...("uhh...unless...well...unless you've driven in the snow/slush...don't use the parking brake, it might freeze.")...

We now live in mostly flat North Texas. I have my MY set to apply the parking brake when PARK is engaged (although it doesn't seem to be doing it...) Do I need to continue applying the parking brake, even on flat ground?

 

[jcanoe]

88xxx here. QUESTION: Does anyone know how robust the parking pawl is on Tesla drivetrains?

Coming from hilly Northern VA, I learned, and convinced my wife and children, to ALWAYS use the parking brake. "Make it a habit, to protect the transmission."...("uhh...unless...well...unless you've driven in the snow/slush...don't use the parking brake, it might freeze.")...

We now live in mostly flat North Texas. I have my MY set to apply the parking brake when PARK is engaged (although it doesn't seem to be doing it...) Do I need to continue applying the parking brake, even on flat ground?

This is a common misconception regarding Tesla vehicles, other EVs. Think of the Tesla vehicle as having a manual transmission but no clutch. There is no automatic transmission, either conventional automatic with a torque converter or a CVT. What there are most commonly are two electric drive units. front and rear. When the Tesla is in D then power flows to the rear (mostly) and front drive unit (some of the time) to propel the vehicle. Reverse just sends a reverse current flow into the rear drive motor (no need for a reverse gear or shift mechanism.) When the Tesla shifter is in P the Tesla will apply the electronic parking brake to the rear wheels. The electronic parking brake is what keeps the Tesla vehicle from rolling.

The Tesla Model Y Owner's Manual is not very clear when explaining the parking brake. When you stop the Tesla vehicle and want to exit the vehicle you should press the button on the end of the right stalk. The Tesla will automatically apply the parking brake and unlock the doors (if the automatic door unlock option is selected in the settings.) While driving you can also apply the parking brake (what used to be called the emergency brake) by pressing and holding the button on the right stalk for three seconds in the unlikely case the Tesla's hydraulic brakes fail. Some Tesla owners get in the bad habit of just opening the driver's door when stopped to exit the vehicle without first pressing the button on the right stalk to apply the electronic parking brake. When parked the Tesla vehicle will show the vehicle is in P and the vehicle will be displayed in angled profile on the left side of the Tesla's display screen. Note that although the Tesla vehicle will automatically apply the parking brake when you open the driver's door you shouldn't rely on this to shift into park.

 

[jeffbco]

This is a common misconception regarding Tesla vehicles, other EVs. Think of the Tesla vehicle as having a manual transmission but no clutch. There is no automatic transmission, either conventional automatic with a torque converter or a CVT. What there are most commonly are two electric drive units. front and rear. When the Tesla is in D then power flows to the rear (mostly) and front drive unit (some of the time) to propel the vehicle. Reverse just sends a reverse current flow into the rear drive motor (no need for a reverse gear or shift mechanism.) When the Tesla shifter is in P the Tesla will apply the electronic parking brake to the rear wheels. The electronic parking brake is what keeps the Tesla vehicle from rolling.

Thanks...but what is an electronic parking brake - what does it do?

 

[Pianewman]

^^^...then why is there an additional step required to activate the "parking" brake? What is the whirring sound I hear when I hold the "park" button on the end of the stalk, AFTER "Park" has been engaged?

I understand the lack of a traditional transmission/flywheel. I incorrectly used the term "pawl", thinking there must be a similar device to lock the drivetrain/axle/wheels.

 

[jcanoe]

Thanks...but what is an electronic parking brake - what does it do?

Instead of a lever or a foot pedal to apply the rear brakes via a parking brake cable (in case the hydraulic brakes have failed) the electronic parking brake actuates the rear brake calipers to clamp the brake pads to the rear rotors. Some electronic parking brakes have an actuator located on each rear brake caliper; other designs using a single actuator and retain the parking brake cable that connects physically to both rear brake calipers. Many new vehicles have an electronic parking brake that you can set by pressing to engage and pulling up to disengage. Some automatic transmissions will automatically apply the parking brake when you shift into Park (these automatic transmissions retain the parking gear with the pawl.

 

[jcanoe]

^^^...then why is there an additional step required to activate the "parking" brake? What is the whirring sound I hear when I hold the "park" button on the end of the stalk, AFTER "Park" has been engaged?

I understand the lack of a traditional transmission/flywheel. I incorrectly used the term "pawl", thinking there must be a similar device to lock the drivetrain/axle/wheels.

The Tesla has no parking gear with a pawl (pin) to lock the transmission in Park. There is no conventional transmission, drive shaft, etc. If there was, with two drive units, there would need to be two separate transmissions and what jumbled mess that would be.

 

[jcanoe]

^^^...then why is there an additional step required to activate the "parking" brake? What is the whirring sound I hear when I hold the "park" button on the end of the stalk, AFTER "Park" has been engaged?

I understand the lack of a traditional transmission/flywheel. I incorrectly used the term "pawl", thinking there must be a similar device to lock the drivetrain/axle/wheels.

I know the sound you mean, not sure what program is executed by the electronic parking brake when you press and hold the button on the right right stalk (maybe calibration?) Anyway, you only need to briefly press the button on the right stalk. When the Tesla shows the vehicle drive status is P you are done.

 

[jcanoe]

Now a caution note: WIth most conventional vehicles that are front wheel drive or all-wheel drive and have an automatic transmission when you park on a hill, on snow and ice, the vehicle is held by the parking gear pawl (front wheels) and the parking brake (rear wheels) if you do are they teach in driver's education classes (also turn the front wheels towards the curb if pointed down hill or away from the curb if the vehicle is parked pointed up hill.) Tesla vehicles can break free, start sliding on even a slight incline if there is even a thin layer of ice beneath the rear wheels. The extra weight of the Tesla vehicle probably contributes to compressing the snow beneath the wheels into ice and then the wheels lose whatever traction they had when you parked. There are videos of Tesla vehicles that start sliding down a sloped driveway or parking space with a minute or two of being parked. (Summer tires make this even more likely to occur since the rubber compound used on summer performance tires get very hard when the temperature drops below 45F.)

There is a service bulletin regarding having the Tesla Service Center add an additional wire harness to the Tesla vehicle so that the front brakes will also be applied when you activate the parking brake. Not sure if this applies, is available for the Model Y.

 

[frankvb]

I know the sound you mean, not sure what program is executed by the electronic parking brake when you press and hold the button on the right right stalk (maybe calibration?.) Anyway, you only need to briefly press the button on the right stalk. When the Tesla shows the vehicle drive status is P you are done.

I'm not sure about that - I would really like to know the difference (if any). Until we have a definitive answer, just to be extra cautious I would always use the 'long hold' on the right stalk when parking on an incline.

 

[jcanoe]

I'm not sure about that - I would really like to know the difference (if any). Until we have a definitive answer, just to be extra cautious I would always use the 'long hold' on the right stalk when parking on an incline.

If Tesla was like other automobile companies there would be a way to ask a question about the parking brake.

 

[Pianewman]

jcanoe: as usual, excellent description of what's going on. I'm still confused.

When I press the right hand stalk once, engaging Park, I see "P" illuminate, at the top of the "P,R,N,D" column of lights. When I press and hold the same stalk, I hear a "whirring" sound, and see a different "P" being illuminated. Isn't this indicative of a second process, the actual "parking brake" (pads/rotor) being applied?

I guess my initial question about a transmission "pawl" being activated is moot at this point...HAHA! My NEW question is: Is it better for me to continue this second button push, to activate the hydraulic pads/rotors "parking brake" scenario, to take the strain off of the front electric motor, which is now in the "Park" position?

 

[jcanoe]

Here is a short video of a Model 3 owner going through the steps of shifting into Park, applying the Parking Brake. At the very end there is a close up of the driver's side rear wheel where you can hear the electronic parking brake activate when the Tesla is shifted into Park. Then there is a different sound, a brief click, when the Parking brake is activated. No clear answer as to the difference between shifting into Park and applying the parking brake but interesting:

 

[MP3Mike]

There is a service bulletin regarding having the Tesla Service Center add an additional wire harness to the Tesla vehicle so that the front brakes will also be applied when you activate the parking brake. Not sure if this applies, is available for the Model Y.

Do you have a link to this service bulletin? I looked and couldn't find it. (I find it highly unlikely that they could just add a wiring harness to make the front brakes work as parking brakes, that would require replacing the calipers.)

 

[jcanoe]

jcanoe: as usual, excellent description of what's going on. I'm still confused.

When I press the right hand stalk once, engaging Park, I see "P" illuminate, at the top of the "P,R,N,D" column of lights. When I press and hold the same stalk, I hear a "whirring" sound, and see a different "P" being illuminated. Isn't this indicative of a second process, the actual "parking brake" (pads/rotor) being applied?

I guess my initial question about a transmission "pawl" being activated is moot at this point...HAHA! My NEW question is: Is it better for me to continue this second button push, to activate the hydraulic pads/rotors "parking brake" scenario, to take the strain off of the front electric motor, which is now in the "Park" position?

It doesn't hurt to apply the Parking Brake. (However, at least in a conventional vehicle, if you leave the vehicle parked with the Parking Brake set for an extended period the brake pads may stick to the brake rotors when you go to release the parking brake. In an extreme case you will not be able to drive away until you free up the stuck brakes.)

 

[MP3Mike]

Is it better for me to continue this second button push, to activate the hydraulic pads/rotors "parking brake" scenario, to take the strain off of the front electric motor, which is now in the "Park" position?

There is no difference between Park, and holding the button to activate the "parking brake". In both cases the rear brakes use an electric motor to clamp down on the rotors. The extra noise is just the mechanism being activated a second time, and essentially doing nothing because it is already clamped.

The motors have no "park" mode/position. So there is no strain on the motor when you are parked.

 

[jcanoe]

Found this thread re the Parking Brake: Your helpful guide to the Tesla Model 3 parking brake

 

[jcanoe]

Do you have a link to this service bulletin? I looked and couldn't find it. (I find it highly unlikely that they could just add a wiring harness to make the front brakes work as parking brakes, that would require replacing the calipers.)

I don't have a reference or link to this service bulletin.

 

[Kzrman]

Can anyone provide any further clarity on what the difference is between park and holding the park button to put the system into a "second mode"?
What mechanically is really happening when using these two modes?

 

[Pianewman]

There is no difference between Park, and holding the button to activate the "parking brake". In both cases the rear brakes use an electric motor to clamp down on the rotors. The extra noise is just the mechanism being activated a second time, and essentially doing nothing because it is already clamped.

The motors have no "park" mode/position. So there is no strain on the motor when you are parked.

So...the obvious question: Why is the Parking Brake activation listed as a separate function?

 

[jcanoe]

So...the obvious question: Why is the Parking Brake activation listed as a separate function?

The video (see earlier post) shows that you can apply the Tesla's parking brake while driving, even pulse the button that controls the parking brake. I would have labeled the electronic braking function, when stopped, as applying the parking brake. Applying the electronic brake function, while driving, would be electronic braking or even emergency braking.