i have a 1990 Jeep wrangler and today was the first day that i had it in the snow. i got stuck going up a hill, and decided to throw it in four wheel drive thinking that it would be no problem. when i did that, nothing changed. my rear tires were still spinnning and my front tires werent moving at all, but when i pulled the shifter into 4 wheel, it clicked like it turned the four wheel drive on. so i dont know why they arent moving. it wouldnt do anything in 4 wheel hi or low.