Incorrect Speedometer Reading

[Mike@Pawleys]

I am in the process of re-storing a 1970 K10 w/4-speed. When I purchased the truck I noticed that the speedometer was around 10MPH off (Slow). This is probably a stupid question and at one time many years ago I knew the answer, maybe. Anyway, is there an easy way to adjust the speedometer to read correctly? I was thinking that you need to open the transmission and change a gear which operates the speedometer cable. Please help if you can.

[towtrucks]

I think you mean a K-5......
Has the transmission been changed or have the tire size been changed? These things make a difference on speedometer readings. Yes, the drive gear(on the output shaft) and the driven gear(on the cable) can be changed.