On a Ford Escort ZX2, I had to change a speed sensor. It is difficult to remove, as it is inaccessible and sits flush with the casing. You must remove the bolt holding the unit in place and disconnect the electrical connector, then it is only held by an o-ring seal beneath the flange that sits on the transaxle casing. Unfortunately, the unit is often seized up in the casing. I had to cut away part of the casing below the lip on the speed sensor with a cutting wheel on a die grinder to get access to the bottom of the flange. Be careful not remove too much material. The o-ring is about 1.4 inch below the sensor, so stay above that, and cut out only enough to access the bottom of the sensor flange with a chisel. Then I drove the speed sensor out of the transaxle casing with a hammer and chisel. Assembly was just a matter of pushing the speed sensor in place, bolting it down and putting the wire connectors together.