Q: So Snow Mode is for Snow/Ice Conditions, but What if on the Highway?

"But if you are traveling with traffic at highway speeds, and there are some snowy, icy bits what mode would you all recommend?" Slow down.

Fizzy said:

This is a moot point. As per the manual:


The locker disengages at city speeds, let alone highway speeds.

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I agree that the “lock” mode disengages at highway speed. This does not mean that the ELSD won’t engage at highway speeds. If you watch the towing video it specifically shows the ELSD working at highway speeds.

As a data point, in snowy conditions, today, I had 4A and 'Snow' mode. Worked extremely well. Was on a 4 lane running 50-60, power going to all 4 wheels, and throttle control mapped so that the throttle is not as sensitive and keeps the revs lower.

Meeker said:

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If you let your front wheels spin freely, they are more likely to be in static friction since the engine isn't trying to break them free. Think of it this way - in any turn, you have the sideways force on the tire trying to break it free, plus any powered wheel ALSO has engine torque trying to break it free. Unpowered wheels will almost always stick to the road longer than powered wheels. So unless you're rally driving on the Trans Canada to Lake Louise 2WD has a better chance of keeping you on the road.
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You are correct that putting extra force on the wheels has a higher chance of making it slip. So yes, that extra force caused by AWD will make it slip more likely. However, here is what you are missing. The force from driving is tiny compared to the required force for steering. It is penny's on the dollar.

This, as once at steady speed, the engine only is there to keep a car going. It overcomes air friction, rolling resistance and internal engine friction. Etc.

But the force on the wheels when you turn is much - much - bigger. The two Laws of Physics here are that a force gives an equal force, and the preservation of energy. The weight and speed determine the kinetic energy that must be 'put around that corner'. You do this by turning the wheel, causing that kinetic energy to be used to cause a small sideways force against the road. How much force? That is determined by the weight/speed and the angle you placed the wheel at. That force is huge.

That also explains why when going to fast you will go straight. The necessary force is too big for the road friction. Similar if you turn the wheel a bit less, you create less force and hence require less friction.

So if you are right on the friction-edge, then that tiny bit of wheel turn caused by the AWD can indeed make you push over the edge. Just like eventually that one single droplet will overflow the bucket. But just as you cannot predict which droplet it will be, you won't feel the exact moment that bit of AWD pushes you over.

But better not to drive on that edge at all, and slow down just a small bit or steer less sharp, as doing that will reduce the friction requirement far - far - more than switching off AWD. If you are that close to the friction-edge, any change on the road will already slide you out of the corner.

The AWD only needs to work hard when the friction to slow the car down is high. But if so, you will not have issues going around that corners as the same friction helps you there.

Add to that on the Expedition the car will switch off AWD in corners anyway at very slow speed (for different reasons), will break individual wheels and throttle the gas when sensors detect you are slipping. The computer will react in fractions of seconds for all these three things.

Still not convinced? Well, that small bit of force the AWD produces, still needs to be put on the back wheels. So you may help the front wheels, but now you get that back breaking out more. After all the engine has to turn anyway, and better to spread that force over 4 than 2 wheels. In fact with smart AWD it can - in theory - actually move all the force to the straight back in the beginning of the corner, and to the front once that is straight. Also better to have under- than oversteer. Oversteer is much harder to correct for most people plus you won't feel it coming unlike understeer which exposes itself through a 'light' steer.

So in practice switching off AWD won't help, and you will lose all the benefits.

my 2 cents, 4 is always better than 2, steering, cornering, accelerating or correcting = all of it. but maybe because i came up on quattro's & mountains of snow, when the front & rear wheels having well distributed drive actually helps keep the vehicle in control under every circumstance, for me, & especially when cornering & needing to correct if the rear got loose or the front lost steering response.

i'm so addicted to 4wd/Awd that i constantly find myself driving these backroads in 4a in wet, even dry sometimes TBH because it seems to handle better / feel more responsive with the front drivetrain engaged.

Bunky said:

"But if you are traveling with traffic at highway speeds, and there are some snowy, icy bits what mode would you all recommend?" Slow down.

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Please read my first post as this is covered.

Expedition Dave said:

Q: So Snow Mode is for Snow/Ice Conditions, but What if on the Highway?

I get that the system is set up for what I would assume: slow going through bad weather--to get you through it.

But if you are traveling with traffic at highway speeds, and there are some snowy, icy bits what mode would you all recommend?

Not a trick question, but I am curious the hive's thoughts and please state why. Please refrain from long talks about safety, snow tires and chains b/c obviously, one must drive the conditions, but curious the opinions here. And also b/c most people who don't live in the snow belt, but drive through it briefly, usually don't run snows but all seasons/ATs (like me lol).

My thoughts that a locked center diff and/or locked rear (unless going through the thicker, less than 10 mph stuff) on the highway or carrying any real speed might cause the vehicle to go into a skid/slide more readily since spinning tires offer no traction, but a tire rolling along will offer some directional stability.

So, I personally feel that AWD and traction control are the way to go, either in SNOW mode or ECO mode to soften throttle inputs for more diffrence ice vs snow here

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The conditions you describe here are the exact conditions that prompted the development of 4A systems. Traditional 4x4 systems had two problems in these conditions; first, on the "dry" sections of pavement the driveline would have a tendency to bind in the turns. Second, on the snowy/icy patches, a throttle impulse can cause a spin out as the torque "steer" on each axle is in the opposite direction which results in a rotational force around the center of the vehicle. 4A systems solved both of these problems by 1) allowing the front and rear drive shafts to rotate at different speeds and 2) reducing torque when wheel spin is detected. Stability control systems built on this foundation by adding yaw sensors, steering input sensors, etc, etc.

In summary: Snow mode for compact snow and ice, 4A for roads with patches of clear and snowy/icy.