This is my 01 F250. 7.3L Got in the truck yesterday to go into town and I heard this rapid clicking under the dash. Put the key in and its to dead to crank fast enough to start. Jumped her off and the noise continues but faster now. Oh well, hit the road. First thing I notice is the OD OFF light in the shifter handle is blinking. Switch works, just blinking. Then I see the speedo needle bouncing like crazy. I go on my way. start hearing a buzzer noise but muffled. Turn down the radio and its coming from under the dash. Oh well finish my mission. Get home and park on the concrete cause I know I'll be going under there tomorrow. come out in the morning and the cargo + int dome light is on too. Watched some you tube vids and it says the VSS is bad (vehicle speed sensor) shows its on the top of the rear diff. Shows how to ohm it out ect. another showed chafed wires leading to that sensor. Put her up in the air. checked all the wires. no problem. sensor OHM'd as good. Pulled off the lift. test drive and the problems gone. Have no idea what I did or what the problem was. I believe it will probably come back again. Anyone have an idea?