Between 1980 and 1983 I worked as a tow truck driver. During that time I towed hundreds of cars using professional towing gear of the early 80's in situations ranging from broken cars, to car accidents, to illegally parked cars, and other police enforcement tows. This was a job I had while going to college, and it sure beat the fast food jobs I'd had previously. While I had the job because my father owned the towing company, I worked in the same conditions as anyone else, working the same shifts.
Let's assume at the outset you've already made sure your tow vehicle has the towing capacity to tow a car, and that you're already comfortable with the rituals of towing a trailer or a car. Understand that your tow vehicle will drive, and most importantly, and back up differently when you're towing something. Heaven help you if you're towing a vehicle that is towing a vehicle.
The bottom line rule to avoid damaging the towed car's drive train is ensuring the wheels on the ground are disconnected from the drive train, and to ensure the parking brake is disengaged. A simple method is to lift the drive wheels off the ground.
The most natural setup for towing a car with a tow truck is lifting the front of the car, and leave the rear wheels on the ground. It's important that the wheels on the ground are not steering themselves as you drive, so that the towed car tracks straight with the tow truck.
All electric car makers recommend towing on a trailer or flat bed. Possibly that is due to overabundance of caution a.k.a. fear of being sued. As we'll see there are a couple technical reasons behind this.
The duty to avoid damage
Over the years I've seen lots of negative assumptions about tow truck drivers, that they're all dirty uneducated bums who don't care about whether they damage the cars being towed. I can only speak to the drivers I worked with in my fathers towing company.
First off, this is dirty work. Tow truck drivers are crawling around on the ground, underneath cars, sometimes those cars have been in bad wrecks and are leaking fluids, etc. Just tell me how a tow truck driver is supposed to avoid being dirty.
It takes a certain mechanical skill to tow cars and trucks without causing damage. The wide variety of situations tow truck drivers face requires ingenuity to solve problems in the moment, involving moving heavy hunks of metal, without causing damage.
Tow truck drivers maybe do not care about the cars they're towing. What they do care about is their insurance premiums and avoiding having to pay for damage caused to a car. The incentive to not damage a car being towed is not from the goodness of his/her heart, but to avoid penalties or legal problems.
That wasn't a tangential divergence, but a demonstration of the risks involved in towing a car. Several tons of metal, if towed incorrectly, can become a missile which could wreak havoc on the road. Anybody towing a car has two duties:
- Avoiding damage to the car being towed
- Avoiding causing inadvertent damage to other cars with the towed car
Towing front-wheel drive cars
The easiest scenario is to simply lift the front wheels off the ground. As long as the parking brake is released the rear wheels will spin freely. Since it is the rear wheels on the ground, they'll automatically track straight with the tow vehicle.
There will be times - like the towed car has been in a rear-end collision - where the front wheel drive vehicle cannot be towed the simple/easy way. Instead the front wheels have to be on the ground, with the rear wheels lifted. In this case you must first put the transmission in neutral, but the big issue is that the front wheels will steer themselves causing the car to swing around wildly.
The car being towed must track straight while being towed. If it does not track straight, it be dangerous, for example by swinging wildly and hitting other cars. Or the car could even break free and roll off on its own. There is nothing more sickening than watching the car you were towing suddenly rolling freely down the road with nobody in it.
If the car is towed with the front wheels on the ground, clearly the front wheels must be prevented from steering on their own. It is not enough to trust the steering lock on the steering wheel. Instead, you must tie a rope to the steering wheel, and secure the rope somewhere, so that the rope holds the steering wheel straight.
Otherwise the front wheels must be put on a tow dolly.
Putting a car "in neutral" for safe towing
The phrase "in neutral" comes from having a transmission. It means to disengage the drive shaft from the motor/engine. Drive wheels that spin freely without mechanical connection to the motor/engine cannot cause damage to the motor/engine.
Putting the car "in neutral" is simple if you have the car keys, can open the passenger cabin, and operate the transmission lever.
But sometimes tow truck drivers must tow the car without permission of the car owner. Usually this is for law enforcement reasons, like illegal parking, or crime investigations. That leaves the tow truck driver with the problem of putting the car into neutral. Some tow truck drivers own "slim jims" or other tools that can forcibly unlock a car door, that some might call burglary tools. My personal slim jim was one time put to use by police officers when I was officially brought in to officially observe the execution of a search warrant on a car owned by an accused house burglar. I learned a certain delicacy that night to opening a car door without screwing up the fingerprints. But, I digress. With some cars you can crawl under the car, disconnect the linkage between shifter lever and the transmission, and operate the transmission manually. If you cannot do that, then the rear wheels must be put on a tow dolly.
Disengaging the parking brake for safe towing
Most/all cars have a brake that's meant to be used, while the car is parked, to lock the wheels so the car doesn't roll down a hill. If the parking brake is engaged, the wheels won't spin freely and if the car is towed the brakes would be damaged.
I do not remember a method to disengage the parking brake without access to the passenger cabin. One solution is to put the car on a dolly.
Towing rear-wheel drive cars
With a rear wheel drive, the drive train connects to the wheels that would naturally be on the ground when towing.
One successful method is to lift the front of the car, leaving the rear wheels on the ground, and to ensure the drive train is "in neutral", and to ensure the parking brake is disengaged. Re-read the sections above about both these measures. If neither are possible, the rear wheels would be put into a tow-dolly.
Another method is to instead lift the rear of the car, leaving the front wheels on the ground. Re-read the section above about tying down the steering wheel.
It seems that flat bed tow trucks are more common than they were in the early 1980's when I was a tow truck driver.
On a flat bed all the wheels are off the ground. Ergo there is no worry about disengaging the transmission etc. The tow truck driver does have to be extra careful about tying the car down with good quality straps. As long as that was done properly the car can be towed with no problem.
If the wheels are locked up - e.g. parking brake - and the tow truck driver cannot unlock them - which I've heard happens to some fully discharged electric cars - the tow truck driver has no choice but to drag the car onto the truck. This is suboptimal, but for the short distance required to get the car on the truck no significant damage is caused.
Putting the car on a car trailer may be the most approachable for the average consumer. With this kind of trailer you drive the car onto the trailer, then tie the car down. Like with the flat bed, all four wheels are off the ground and the only consideration is ensuring the car is securely tied down to the trailer. There is nothing more sickening than to see the car you were towing suddenly rolling freely down the highway with nobody on board.
A variant of a full-on trailer is the tow dolly. This is like a short trailer, that holds just the front wheels. You drive the car onto the tow dolly, and then tie it down.
The biggest problem with either is the risk of accidentally messing up while driving the car onto or off of the trailer or tow dolly. You could miss the trailer then be in a sticky situation where the trailer is wedged under the car and cannot be removed.
Flat towing a car
With flat towing all wheels are on the ground. It seems this is the easiest way of towing a car. All that's required is having a secure hitch arrangement at the front of the towed car, and ensuring all wheels roll freely without damaging the drive train.
It's also necessary to prevent the front wheels from steering while being towed. In other words, one must tie down the steering wheel (see above).
Towing an electric car - flat or otherwise
Now that we've talked about the general principles of towing a car, let's talk about electric vehicles.
The biggest difference is that electric vehicles cannot mechanically disconnect the wheels from the electric motor.
Because gasoline cars must idle when stopped, and because they must use gearing to go into reverse, and because they must use multiple gears, they must have a mechanical disconnect between wheels and the engine. Electric cars do not idle when stopped, they can go into reverse without a reverse gear, and often do not have multi-gear transmissions.
The "Neutral" mode in an electric car is not accomplished by mechanically disconnecting the wheels. Instead "Neutral" is a setting in the motor controller that turns off both acceleration and regenerative braking.
What this means is, the electric car could be hooked up to a tow truck, the parking brake disengaged, the "gear selector" set to "N", and the wheels apparently rolling freely, but the wheels are still connected to the electric motor, which will cause the electric motor to spin while the car is being towed.
It's one thing for the electric motor to spin when the car is coasting. For short distances in traffic a little coasting will be fine, but is that safe over a long period of time like when towing?
With a front-wheel drive electric car, like the Nissan Leaf (2013+ model years), it is possible to tow on a tow-dolly with no problems. Make sure to disengage the parking brake. Double check with the owners manual of your car for manufacturer recommendations.
Wait, isn't towing with the electric car turned on equivalent to coasting down a mountain? Wouldn't that simply recharge the battery?
To those suggesting towing an EV could recharge the battery pack thanks to regenerative braking. STOP. THINK.
If the car is turned on, ready to drive, set to "N", set to turn off regen, that combination is as close as possible to "Neutral" for an electric car. This mode is often the best way for driving down a mountain. But we're talking about towing, not coasting down a mountain. The difference is in the distance traveled. A mountain near me allows 10+ miles of coasting from the top to the base, and you can regenerate a LOT of electricity that way. But a long distance tow can go for 400+ miles per day.
Reread the previous section. In an electric car set to this mode the electric motor will be spinning while coasting or being towed. Will the manufacturer have designed it to allow for coasting a couple hundred miles at a time?
What about towing an electric car to recharge it? Apparently a bunch of folks have done this. I would not do this for any large distance since it is so inefficient and will cause the tow vehicle to consume way more fuel than normal. The manufacturer will not have designed the regen system to be used this way, and it might damage the regen circuits. Normal regenerative braking usage is not continuous for hours at a time.
Flat towing an electric car - disconnecting drive shafts - or maybe not
In the MyNissanLeaf forum, Tony Williams said it is possible to "disconnect the drive shafts" on the Nissan Leaf between the wheels and the motor, then to flat tow. These are the "half shafts" that go from each wheel to the drive motor. In other words, while these cars do not have a normal mode to disconnect the drive wheels a mechanic can possibly physically disconnect the drive shafts. See: https://www.mynissanleaf.com/viewtopic.php?p=185185#p185185
In the MyNissanLeaf forum, "Ingineer" (a.k.a. Phil) said -- IN THEORY -- it is possible to flat tow a Nissan Leaf so long as it is turned on and in "Drive". The car will become fully charged with regen, and once fully charged the charge controller will turn off regen and everything is fine. As smart as Ingineer is, and he knows a lot about these cars, this advice should be taken with a few grains of salt. See: https://www.mynissanleaf.com/viewtopic.php?p=185574#p185574
That same forum has dozens of folks saying putting a Nissan Leaf on a tow dolly, or otherwise lifting the front wheels, is the best method. The Leaf is a front wheel drive, hence lifting the front wheels ensures the front wheels are not being turned and therefore do not turn the motor. Of course, ensure the parking brake is disengaged.
This same technique should work with other front wheel drive electric cars. You should of course check with the owners manual to be certain.
All wheel drive
Some electric cars have all-wheel-drive. They aren't front-wheel-drive, nor rear-wheel-drive, but instead all four wheels are connected to a drive motor. Often there are two drive motors, and could even be four drive motors. This is great for handling and efficiency, but throws a kink into the plan just discussed for towing electric cars.
Unless the manufacturer has a recommended towing method, it would be best to tow these cars on a trailer or flat-bed truck.
http://www.remcotowing.com/ -- Maker of tow hitches for flat-towing all kinds of cars. For every Nissan Leaf model year their guide says it must be towed on dolly.