I have  a 1998 qcsb 4x4 5 speed and I noticed a slight movement in the tach needle at all rpms. It has done it since I bought it back in april and was wondering if it might be a warning sign of a sensor on its way out. It only moves about the width of the needle and I cant feel and change in speed or engine noise. I am going on a 3 week trip at the end of the month and thought that I might bring a spare but I don't know if it would be, the crank or cam sensor. All of my other trucks seem to have a rock solid tach needle but this has me bugged.

Tach is following crank sensor. Could be a sign

Thanks, that is what I thought. I plan on taking one on my trip just incase.