We had another 20 cm (eight Merkin) overnight. When I dropped my daughter off to school for a sports event this Saturday morning, there was a older Toyota Yaris stuck in the snow in the parking lot. It looked like maybe a 2012ish model.
People were trying to remove the snow from under the car, and we tried pushing it a few times. The back wheels were spinning on the snow, which from my limited knowledge of AWD, this shouldn’t happen. We tried having some people sit in the back where the hatch comes down to add some weight, and it managed to only have one of the wheels spin. The front wheels never moved.
Eventually, about eight guys got involved and we were able to push the car enough to get it free.
Yeah the Yaris is and always has been front wheel drive. If it was something like a Rav4 then it seems unlikely that only the rear wheels would be spinning. Maybe a (very old) Corolla or something? Or not a Toyota?
If the front wheels never moved, my first reaction is that the car was actually an RWD car that was not in fact AWD / 4WD equipped, or the front drive train was switched off or failed.
Some very primitive AWDs had anti-slip between left and right on each axle, but not as between front and back. So if you got one end in the air, that end got all the torque and the other end got zero. But I’m talking 1970s gear, not 2010s. Never say never for a cheap enough car, and a Yaris (if that it be) was certainly their bottom of the barrel design. As unlikely as that sounds to me, it’s a result that fits the apparent facts of the matter as best we know them.
aside:
If any 2WD car is high-centered enough, having both drive wheels spin is unsurprising. They both have so close to zero traction that there is no back torque to drive the anti-slip features. If, as you did, you got one drive wheel connected to the ground at least some, that one should have gotten the lion’s share of the available torque. Should.
Maybe a Vitz then? Wiki says the Yaris nameplate wasn’t introduced to Japan until 2020.
I can’t find much information on the Vitz AWD system, but it doesn’t look like it had a locking center differential or a limited slip on either of the axles. So power would flow to the path of least resistance, which would explain the one wheel peel. I don’t really trust the information I’m seeing, though, it’s all 2nd hand.
I like watching videos where people test all (and 4) wheel drive systems by putting some of the tires on rollers. The equivalent test for what you saw would be the rear tires on rollers, forcing the AWD system to move the car with just the front wheels.
Some of the systems fail. They are unable to direct adequate power to the wheels with traction, so they end up spinning the tires on the rollers. Sometimes this is completely expected, like a 4WD system with an open differential and no electronic traction control. Other times there is some sort of torque vectoring AWD system, but it isn’t up to the task.
Sometimes it seems that the traction control is fighting against itself. It may brake the spinning wheels, but then cut power because it detects wheel spin. Which means the car never gets enough torque to the wheels with traction to move the car. Often, but not always, this can be helped by turning off traction control, or picking different AWD modes.
Right, 2WD without “limited slip” is really 1WD when conditions are right. Without a locker or specialised gear train 4WD can be 2WD for the same reason.
AWD (all wheel drive) is not the same as 4 wheel drive. The various systems work with the antl-lock brake system to keep the tires from spinning. The spinning tire gets a brake so the other tires can attempt traction. Sometimes you can feel like you are sitting in one spot while the brakes and the traction fight each other. If you have the option of turning traction control off, or locking the car into a 4 wheel drive mode, you may have a chance of getting unstuck.
AWD is great for maintaining control on a slick surface, like driving down a frosty road. But it is much different from actual 4 wheel drive.
Is that how it’s done? Braking? Makes sense. Back in the dark ages of RWD it was sometimes possible to get the differential to apply power to the non-spinning wheel by slightly applying the emergency/parking brake.
I got stuck once upon a time in a AWD Audi - parked where there was a decent amount of packed snow, so the underside was hung up on the snowbank and the wheels just spun I had very slight traction, so about 5 or 10 minutes of back and forth (starting with maybe an inch travel) I finally got fre.
If it was just that simple. AWD is a marketing term only and there are systems that are called AWD that many would really consider 4WD, and also the other way around. So instead of just looking at the badge one really has to know which system they really have and what’s its strength and drawbacks.
By design all wheels are powered, but in the way guaranteed to be least useful in low-traction situations. IOW, AWD in name only - pure price engineering.
I’m a little surprised such limited vehicles are still being made by anyone but Chinese and Indian companies specializing in the needs of the poor world. I’d have expected a lot more from a Japanese make in a Japanese market. That’s a world class company selling into a world class society. Color me bemused.
I think the Vitz uses the Toyota ATC/DTC all wheel drive system. I think, if I understand correctly, it does not use a 4x4 style transfer case, but the power for the rear is (maybe?) taken from the front differential and transferred through an electromechanical coupling to the rear differential.
Older models of Vitz are similar, but use a fluid coupling.
In normal situations the car is front wheel drive, but if the front wheels slip, the car will engage the coupling, and send power to the rear.
I don’t want to deny the OP’s report of what was happening, I just don’t understand how this system would allow it to spin both rear wheels, but not the front. I would expect it to spin one wheel in the front and one in the back. If the front wheels are not spinning, then no power should be sent to the rear. Perhaps 1 front and both rear wheels were spinning?
So
1 wheel spins — no problem, power sent to other axle
2 wheels on same axle spin — no problem, power sent to other axle
2 wheels spin on opposite axles — problem, stuck
3 or 4 wheels spin — problem, stuck
This is the reason that I wrote the OP. It doesn’t seem to make sense.
When I arrived, the adult male driver, my friend “Hiro” (who was there dropping her other children off), Hiro’s 13-year-old son and a high school boy were trying to shovel the snow out from under the car. They had put some sort of material under the rear tires for traction, but that had failed.
I joined, and another high school boy as well.
At some point, Hiro got in and tried reversing the car while the rest of us pushed.
This is when both rear wheels were spinning, but the front wheels were not. I was pushing on the front and could hear both back tires spin, which I confirmed when we gave up trying to push it free but while Hiro was still trying to back out.
After another adult friend showed up, dropping his son off. After removing some more snow we tried having Hiro and her son sit in the “trunk” with the hatchback door open to add some weight over the back tires. This is when one of the back wheels was spinning and the other wasn’t.
I was at the back of the car and could verify that, and it didn’t seem that the front wheels were spinning, but I can’t be 100% certain.
After that, word had gotten out and several other people came to help, and we muscled it free.