I was wondering where the Speed sensor for a 98 dodge ram pick up is?

My check engine light is on, okay, my first code reads "cylinder 1 misfire". Which a couple of years ago it was accurate. I changed all plugs and wires, and the problem was fixed, but check engine light would not shut off. Now I need to get the smog done and now there is two codes "cylinder 1 misfire" and " Speed sensor malfunction". My truck is running perfectly and I need to find out where the "speed sensor" is so that I could clean it and try to get that check engine light off for smog. Thank you guys....