Speed Sensor Disconnect for Nav Unit

[BernieB]

I've seen a number of posts to cut the speed sensor wire from the rear of the nav unit so it can be operated at speed. 2 questions:
If I disconnect it, will the manual transmission "speed matcher" for shifting be affected and where is the other end of the wiring harness if I don't want to have to pull apart the whole dash. It would seem to be easier to get to that wire somewhere else along its run.