From: "George (Andy) Anderson"
Date: Fri, 1 May 1998 00:29:48 -0500 Subject: Re: Wanted: 19 Tooth Speedo Pinion Gear and Sun Visor On 30 Apr 98, Michael Foerster wrote: > Does anyone have a 19 tooth (White) speedometer pinion gear? I > have a 17 tooth and my speedo is off. Mike, having recently been through this myself, I have a bit of advice: what you really want to do is make sure that your odometer is correctly driven by the pinion gear. Probably the easiest way to do this is to find a road with mile markers and see how much your odometer varies from the mile markers over, say, 6 to 10 miles. If your odometer is really 11.7% *high*, then going from a 17 tooth pinion to a 19 tooth pinion would correct it. Note that increasing the number of teeth on the pinion gear will decrease the indicated speed and mileage. Once you have the odometer calibrated correctly, you can check the speedo to see if it is off. If so, you can remove the speedo from the car and calibrate it with the small spring that returns the needle to the rest position (0 mph). Once you remove the speedo from the dash pod, you will notice that the pointer return spring is attached at one end to the speedo pointer, and at the other end to a small arm the is held in place by a small nut concentric with and underneath the speedo pointer. You might be able to move the little arm without loosening the nut, or you might have to loosen the nut *slightly*. If yours is like mine (I have an '83 280zx n/a, but with a '79 280zx, 130 mph speedo), a small movement in the little arm will result in a moderate change in the tension on the spring which in turn results in a moderate change in the indicated speed for a certain input speed from the pinion gear. This does, unfortunately, involve a bit of trial and error. What I did was calculate how far off my speedo was, percentage wise, which turned out to be about 13% too high, then used a plug-in type electric drill (not a battery powered one; you need to be relatively reproducible) to spin the speedo (you need a reversible drill turning in the reverse direction), noted the indicated speed, and adjusted it until the indicated speed was 13% less than that. YMMV (no pun intended). This takes a lot of words to explain, but if you look at a speedo unit for a while and play with it a little, it should become clear. You might consider getting a speedo unit of the same year as yours from a junk yard just to play around with before doing anything to the one in your car. Good luck!