Where are the speed sensors located on a 1999 Mercury Cougar?

This part sits on top of the transmission. Look just behind the intake manifold. It is not easy to get to. Suggest you get a transmission shop to handle the work...probably less than $200. If you are trying to do this to correct shift problems, suggest you on wrong trail...try a shift control unit, which is located near the speed sensor. Unless your tachometer and speedometer are acting up, look at the shift control unit. It does seem to go out after 100k.