This morning the road surface was quite icy around here. At the school parking lot I saw someone forgetting a basic rule of winter driving: if your wheels are spinning and you’re getting nowhere, stomping on the accelerator will only let you get nowhere, faster.
Now, when a standard transmission car won’t start moving because of slippery conditions, it often helps to shift the car into a higher gear and try again. (That’s what I had to do.) What do you do if a car with automatic transmission gets stuck in a similar situation? You can’t shift up!
That’s why people in areas with severe winter weather often shun automatic transmissions. I grew up in Hanover, NH where manuals outnumbered automatics by a decent margin, counter the trand in most of the country.
To get around what you mention, many new cars come with a “winter mode” on their automatic transmissions that tries to imititate the behavior of a manual by starting in second gear, shifting earlier and more slowly, etc.
Well, I would say you don’t want to be in Drive. All automatics allow you to select first gear, which at least keeps it from shifting when you don’t want it to. Many allow you to select second, presumably for just the situation you describe.
If you select second gear in an auto tranny, you still start moving in first; it just prevents shifting past second. I know of now way to force the tranny to start movement in a higher gear than first.
As racekarl said, many luxury cars come with a winter driving mode button, that will force the auto tranny to use 2nd gear instead of 1st when starting to move. Without that feature, you just go real easy on the gas.
I think it’s begining to filter down to less luxurious cars.
Yes, many cars will now actually start in second when the auto trans is set to “2”. Often, there is no fancy selector button. Just shift 'er into “2”. Often, no higher gears than 2nd can be selected as the starting gear.
My wife’s 2000 Honda Civic works just like Philster describes, complete with an explanation in the owner’s manual.
It’s a four-speed auto, with gear selections P-R-N-D[sub]4[/sub]-D[sub]3[/sub]-2. There is no first-gear-only selection.
D[sub]4[/sub] is standard “drive”, allowing the tranny to use 4th gear (which I believe is an overdrive gear). D[sub]3[/sub] is basically the same thing, with 4th gear locked out.
“2” is 2nd gear only - even when starting from a standstill. The manual indicates that this is useful when starting in slippery/icy conditions (something that is only discussed in the abstract in Southern California :)).
I have trouble understanding this, too. Even given that a gearbox (auto or maual) is designed to provide power and speed in different ratios for different conditions, driving off from a standstill on an icy road is purely a matter of delicate speed control. I guess what I’m suggesting is that what is the difference between starting off in second, or starting off in first with relatively less gas applied? The rotating wheel on the ice doesn’t know what gear you’re in.
In icy conditions, the traction of the drive wheels can be insufficient to overcome the inertia of the vehicle. This problem compounds itself because spinning tires are more likely in places where people have spun once already - the spinning tires warm compacted snow up enough to put an icy crust on it. Intersections and parking lots can get really bad in the absence of sufficient sand or salt. By using a higher gear, you’re giving your engine less leverage, in a sense, and so you have a slightly better chance of transmitting drive force to the road instead of breaking your tires loose.
Myself, I just avoid automatic transmissions like the plague. This situation isn’t the only one where they’re not ideal. Plus it’s just more fun to drive a standard.
It’s true that the drive wheels have no way of knowing what gear the transmission is in. However, the slope of the “torque-vs.-throttle position” curve (yes, I made that up) is much steeper in a lower gear. In a lower gear, the range of throttle positions that give enough-but-not-too-much torque is smaller than in a higher gear.
When traction is poor, and “too much torque” isn’t all that much, this range can be very small indeed. Selecting a higher gear flattens the curve, widens the throttle position range required, and requires less delicacy on the throttle.
True, but the Golden Rule for driving in ice and snow is All Things In Moderation and it is much easier to be moderate with the power applied to drive wheels on starting if you are in a high gear rather than a low one.
I just thought of a nice analogy for those who aren’t following.
Imagine you’re on a mountain bike on a gravel surface. You’re in the lowest gear, and currently not moving. Now, if you jump on the pedal, what happens? Your rear wheel spins, shooting gravel out the back, and the bike doesn’t move much.
Now shift into the highest gear and jump on the pedal. What happens? You don’t spin, and begin moving, albeit very slowly.
It’s a question of whether there’s enough torque at the wheels to break the tires loose. The higher the gear you’re using, the less torque there will be at the wheels, other things being equal. So on ice in your car, in 1st gear even at idle the wheels might spin when the transmission is engaged, while in a higher gear, the wheels might not spin unless a fair amount of throttle is applied. This makes it easier to get the car rolling using 2nd, or even 3rd if you’re driving a 5 speed.
I drive a rear-wheel-drive automatic and get stuck now and again. I just drop it into reverse, then drive (repeat as necessary). If the snowbank behind me is tall enough I drop into neutral and roll back to my starting point and some.