Why 10.7 volt input at ‘71 Duster instrument panel?

Update on speedometer. With the cluster on a bench - I used a drill to run the speedometer up to mid 30s and there’s no clicking. I then jacked the back wheels off the ground and ran the car in 3rd gear and the disconnected cable made no noise. I reconnected the speedometer and ran the car in 3rd and the clicking noise came and went as I applied pressure to the plastic connector that clips to the speedometer. I’m thinking that my next step is to buy some lubricant and apply generously to the cable. I just read a suggestion that I use spray white lithium grease. Any other suggestions at this point?