On Sunday 15 November 2009 17:56:01 teseract@moparhowto.com wrote:
> This being my first winter driving a RWD/4WD vehicle (I've always driven
> FWD cars until this point), I thought I'd ask for some opinions as to
> braking technique.
IMHO, the most important thing to remember is that all cars have four wheel
braking. Engaging 4x4, you'll find you have more traction to *go*, but that
doesn't increase your traction to *stop*. Until you get used to that, be
careful you don't get overconfident. I see a lot of "4wd" SUVs in the ditch
around here after the first couple of snowfalls when people punch the 4wd
button, find that pushing the gas pedal works great, and go zooming off. It's
only later when they try to turn or stop that they find that they're no better
off than the guy in a 2wd.
> My '95 4x4 is an automatic and has 4 wheel ABS. My father, when driving a
> RWD automatic car, always kicked the car into neutral under braking in
> snow/ice covered conditions as it kept the rear wheels from "pushing"
I drove for many years in a big, heavy RWD automatic car. Popping it in to N
while braking sounds like a really bad idea to me. You're more likely to lock
the rear wheels than the front, which is the same reason that even entry level
trucks get rear wheel ABS. But if all goes well, you don't want to lock *any*
wheels. If your truck has four wheel ABS, that's good and should keep you from
loss of control due to a slipping wheel.
> Now, with ABS I'm not sure if this is true, as if you lock up all 4 wheels
> while in "N" the ABS has no way to know the vehicle is still moving, right?
Think about where the sensors are. They don't mount them on the engine or
transmission, so the transmission doesn't have a lot to do with it.
> If it's slick I'll be in 4 high of course, so if the front wheels lock, the
> rears would be forced to as well due to the diff being locked, no?
Your front diff doesn't lock, it's open. The centre probably isn't a diff,
it's just a gearbox, so it's locking the front and rear driveshafts together.
Your rear diff may or may not be a limited slip design, you should check to
find out for sure. So in "4wd", you may have one or two wheels not actually
driving the truck, depending on what rear diff you have. Keep that in mind as
well.
> how does the ABS even know to engage? All I can figure is you have to be
> light on the pedal even under emergency braking to get the full benefit of
> ABS?
If ABS is engaged, stand on the pedal and let the computer do its job. If you
let off the braking pressure, the ABS could disengage, thinking that you're
done braking. If you want to stop, the last thing you want is to get off the
brakes.
> So I guess I'm just looking for the best way to brake with 4 wheel ABS, an
> auto trans, with 4x4 engaged, on ice/snow...
Andy's right, find an empty parking lot and practice for a while to get used
to it. There's no substitute for experience and practice.
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