The "W" is for Winter, not Wet. It alters the TCU to start off in second gear instead of first.
I did the same thing in a '67 Camero on the way to Denver when I was about your age, it had just started snowing to the north of Dallas,
I came up behind a Cadillac going maybe 20 MPH, pulled out to pass him and when I pulled back over I did 2 or 3 360's and luckily got it straight again without touching anything. I can still remember the look on the Cadillac drivers face each time I came around !