It's mounted on the trans on the end or the shifter shaft. The shaft rusts and locks the sensor up causing it to be hard to shift. It's easy to replace, disconnect the shifter cable, remove 2 bolts, then the cable connector. It should then come off, but mine was rusted solid to the shaft, I pried it off with a crowbar. I've got the shaft soaking in Naval jelly with a rag around it, I'll finish it up today.