jrfiero

Thoughts on using Neutral or Drive going down a slippery, snowy driveway?
Our driveway is hardpacked snow, not plowed or shoveled through two blizzards and several other small events. It has a significant slope, with a curve for good measure, and woods down off the outside of the curve.
So, my thought is that in neutral I get more even braking from all four wheels than when in drive, since our AWDs are primarily front wheel drive and the front wheels would be pulling at least a little.
This is obviously going down forward, not reverse, although my thoughts would be the same.

Snowing right now! I drive the RX down out of the driveway, then drive my AWD van (parked down off the street) up and down a couple times. That's my snow "clearing" technique! May have to rethink it - first winter in this house. Have you priced tractors lately?

Jonas

Gatriel

Can you put it into tiptronic mode and stick it in first? Seems like using Engine compression + brakes as a backup would be the way to go.

budwom

I'm with you. I drive in snow all the time, and engine braking is our friend. A nice low gear as you descend is the way to go.

In really bad snow on an interstate, i'll often go into third gear and plod along at 40 mph or so, very effective.

kitlz

Jonas, if you put the RX in neutral, you lose the ability to have the engine help slow you down. Try using a lower gear like everyone has suggested. I'll do that on the many hills I have to travel. At least you don't have other vehicles to worry about. Have you looked into a plow for the van It's snowing here too. Be safe.

corradoMR2

Yep, as everyone stated, use engine compression as it's much safer controlling the speed downhill.
Move the shifter to "S" and downshift to 1.

Also, if you have AWD, engage the center differential lock on the center console just below the Remote Touch controller so compression is distributed to all four wheels.

jrfiero

"Yep, as everyone stated, use engine compression as it's much safer controlling the speed downhill.
Move the shifter to "S" and downshift to 1."

How is this safer (never mind "much" safer)? As I mentioned, engine braking will primarily act on the front wheels rather than the brakes that work on all four wheels.
Those of you who are using lower gears are affecting the primary driven wheels, which is usually two of them unless you have a full time 4WD rather than an AWD.
I hadn't mentioned I have a 450h, where there is no mechanical connection to the rear wheels, but I feel the question is equally relevant to the 350 which is primarily front wheel drive. I was not, however, aware of the "center differential lock" on the 350.

I do use Snow Mode, but I doubt that's relevant to the current discussion.

"Have you looked into a plow for the van "
I have! It's a GMC Safari, so I'd think a plow for an S10 or S15 would work, but I don't see any. I can get a lightweight plow that fits in the rear hitch receiver, but I can't see myself plowing the driveway and road in reverse.

corradoMR2

http://www.drivingtesttips.biz/what-...e-braking.html

jrfiero

Interesting link from a UK source I can't identify.

It only repeats the opinions others have posted, doesn't address my concerns.
I'm talking about speeds below "engine braking" - where the engine in drive or another forward gear is trying to move the car forward faster than I want to go.
In the days of mostly rear wheel drive cars it made sense for slowing down because engine braking would use the rear wheels to slow the car while leaving the entire front wheel "circle of traction" to steer the car. In front wheel drive or AWD that no longer applies, especially because I'm not talking about slowing down.

Frankly, I'm sorry I asked.

kitlz

Don't be sorry. The 450h has VDIM to assist in slippery situations. There's more information about it in this thread. VDIM will react far before you will. If it wasn't for the flash on the dash, I wouldn't know anything is going on. The correction is undetectable. It should help you get down your driveway. BTW, skip snow mode. Manually shifting is much more effective.

Droid13

Since you have an "h", I'd say makes no difference, leave it in D and just take it normally slow and careful as the situation warrants. At slow/careful driveway speeds the amount of engine braking (or more correctly, regenerative braking in the case of a h) is negligible and the electrically driven forward creep which simulates a regular automatic in D is also negligible and is really only present at the slowest of speeds and is cancelled by the brakes in most situations especially at anything but creeping speeds.

For a regular RX, as long as brakes are good all around, they will easily manage the normal minor forward pressure without issue. Long, long time ago when I was 16 I had a RWD beater that only had good front brakes. There was a couple of times I hit the brakes, the fronts would lock up but the backs would keep pushing me forward, hard to hold back a RWD V8 when there's no brakes left on the back. Ah, those were the days!

vlad_a

Snow mode is relevant because the rears will get more priority in the h.
Just put it in drive and go. I find electric torque to be better for going through the snow as it doesn't have the same spring-like effect of torque-converters in conventional automatics.
If you are going downhill and the vehicle can move on its own, I would put it in N. You want all of wheels as relaxed as possible to maximize control of the vehicle. Otherwise, force introduced on the wheels to move them forward or to brake, will cause slip, and we all know slip means no control. VDIM will compensate, but it has its limits.

For me, I don't really care. With snow tires on our RX450h, I just turn the snow mode on and drive off. RX does its thing.

Now, the STi is a bit different.
I stop at the top of my driveway. Put the center diff into an Auto+ setting for a more locked center diff.
Get the RPMs to about 3K. Then slowly release the clutch while flooring it.
Yell BANZAI and off we go!
At the bottom of the driveway, ease off the gas, jerk the wheel to the left, which is where I want to go, let the stability system with torque vectoring turn the car in its spot and then floor it again.
Walk with a large grin for the rest of the day.

mkeeney

I don't agree with this at all. In a front wheel drive vehicle, you will only get braking to the front wheels if using only compression braking. If you lightly apply the brakes your braking force is distributed across all four tires. It is much easier to control the braking force using the brake pedal than using the engine. Compression braking will give you one set force based on the current vehicle speed and the gear you select. That force will decrease as the vehicle slows toward the engine's idle speed. You can't change that, and you can't adjust it. Also, ABS can't control engine braking at all.

I just did this same exercise last week in Georgia of all places. Our driveway was covered in packed snow with a slush base, so it was very slick. At the top of our steep hill I slid off the driveway in my 4WD pickup. I backed up into the driveway , put the truck in neutral and let it creep slowly down the hill. The trick is to never get up enough speed that you have to brake hard enough to lose traction. By having the truck in neutral, the brakes were not fighting against the engine. Once you've lost traction on all four tires no amount of electronics will save you. Friction is friction, and braking force is braking force no matter how it's developed. It's best to distribute that force among all four tires instead of just the drive wheels.

RXinNJ

Another problem with this link is that the same advice cannot be applied across all drivetrain types. If you downshift a RWD car in the snow, the rear end can break loose as you increase the torque to those rear wheels. I was amazed at how easy this is to do in my G37x, which is marketed as an "AWD" car, but in reality is a RWD car that converts to AWD as needed.

paul29

If you are going down hill and it is slippery with ice or packed snow the engine compression can slow the wheels to the point they can be rotating slower than the speed you are travelling ie sliding . You then have no steering control as you are sliding unless you go to neutral and allow the wheels to come up to the speed you are travelling, you will probably be in a ditch at that point. By using the brakes you can get rid of the retarding effect quickly if they start to slide, and then regain steering control. Then go back to the brakes. There are some hills you should not attempt as there may be no way to control the decent. Gravity wins.