RE: Auto Xmissions & Winter Driving

[michael_kohlbrenner@xxxxxxxxxxx]

From: rfg@domain.elided
>
>  It is about automatic transmissions and winter driving.
> ...I always thought that if you put
> an automatic transmission into  "L", "1",  or "2", that this
> provided increased torque to the driving wheels and was a poor
> choice for driving in the snow and/or for getting your car moving
> if you were stuck in snow.  Am I wrong?
> 
>   I ask because a recent letter from a reader published in a
> Washington Post column called "Dr. Gridlock" advised that the 
> best way to do this was to use the lower gears.

The answer to this is a big, fat "It depends..."

These days, many automatics are set up such that if you
select some of the lower gears, you will get ONLY that
one gear.  This is probably what the good Dr. is thinking.

For example, I know that many Japanese cars these days
with 4-speed automatics have " D4  D3  2  1 " as forward
selections.  If you select either D4 or D3, the car will
start from a stop and shift up through the gears normally.
The only difference here is that D3 disallows the upshift
to 4th.  If you select "2", however, you only get 2nd.  It
will start in second and then refuse to shift either up or
down.  Selecting "1" gives similar behavior.

With this setup, selecting "2" is the recommended choice
for starting in slippery conditions because this disallows
1st gear and reduces wheel torque at startup.

In my '88 535is, which regrettably has the infamous auto
tranny, there is the "selectomatic" (or whatever they call
it...) switch.  A solenoid forces you to begin in the "econo"
setting which shifts at some ridiculously low rpm.  "Sport"
allows you to run right up to redline.  Then there is the
third setting, " 1 2 3 ", which does exactly what I described
above -- you can set it to "3" if you want and start from a
stop in 3rd and run all the way up to redline at approx.
90 mph.

So, you are correct, in principle, but Dr. Gridlock is
probably also correct in practice, since probably the vast
majority of auto trannies these days have some sort of
"start in second" feature designed into them.

Regards,
Mike Kohlbrenner
'88 535is -- dreaming of a five speed...

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