2006 Lariat V-10, F-350 automatic 4x4, speedometer is intermittent

[magnum136]

I am trying to locate the source of my speedometer problem. I have a 2006 Lariat V-10 4x4 F-350 with automatic transmission with all options including on-board computer for estimating gas mileage, etc.. My speedometer is intermittent. Im trying to locate the VSS (in one or more locations) and was told the speed sensor (VSS) was located on the center of the rear drive axle. I unplugged the 2 wire harness located there, and the speedometer kept working (intermittently) as before, except the ABS Light came on (on the instrument panel) and stayed on all the time, when I test drove the vehicle and when I was sitting still. Keep in mind the 2-wire harness was unplugged from the rear drive axle this entire time.
It seems every mechanic Ive talked to gives a different location for the VSS on my truck. One even told me that there were three VSS on my truck because it is a 4x4. Im trying to narrow this down. Need Help. Thanks