Hello all. I tried searching but couldn't find an answer. The speedo quit working in the 1980 Z. I did the cable spin and the gauge worked, so I went to the next easiest and changed the driven gear. Got the correct color and number of teeth, put it in and it still doesn't work. Next step is drive gear. Is there any way to tell the color/number of teeth without actually pulling the tailpiece? I don't really want to pull it more than once, and my son doesn't want to not be able to drive it while it's waiting for the part. I tried the formula on the TCI site but I'm not sure my algebra came out right. It has a 22 teeth driven gear, the formula comes up between 8 and 9 teeth on the drive gear, a little closer to the 9 side. Then on one of the threads I found searching said something about a 3:1 ratio which would make the drive gear 7 teeth. Any help is appreciated.