Hello, new to the forum here . I have a 1997 F250HD 5.8 manual transmission truck where the tach does not work on startup, but after awhile (5-10 minutes) it works (or seems to) just fine for a bit then stops working. I did have a bad speedometer, and ABS light on, but replaced the VSS in the rear diff and that cleared up the speedometer and ABS issue. My thought is that there must be tach sensor, but I have no idea where it is located. Any help would be much appreciated. Or other things to check first. BTW the truck runs great no other issues I am aware of. Thanks!