Why 10.7 volt input at ‘71 Duster instrument panel?

I came up with an idea while reading another thread where someone with a similar car corrected a speedometer clicking noise by replacing the speedometer gear (at the transmission). I’ve already ordered a new one. As a side-note ….in the late 80s the speedo gear stripped and I got another one from a salvage yard. I was ignorant of the importance of color and replaced a 34 tooth green gear with an orange gear (probably 40 tooth). I learned later that the speedometer was reading about 10% low. I’ve lived with that discrepancy for the past 25 years. It will be nice to get the correct 34 tooth speedo gear even if it doesn’t fix the clicking problem. I’ll pull the orange speedo gear to see if it has any visible damage that might be causing my clicking issue. I could even run the speedo with a drill from under the car to see if the speedo clicking noise goes away.