C6 speedometer cable drive gear?

[Knuckledragger]

I have a 1985 F250 with C6 and 3.54 rear end and stock tires (235/85 R16), but apparently wrong speedo drive gear. My speedo says 80 when I am going about 70, the differences are about 10% off all the way through the speeds. I guess the 4.11 gear somehow got on my drive cable, now I need to know which gear to use to replace it. Color? Number of teeth? Part number? I am racking up way more miles on the odo that in reality.

 

[IDIBRONCO]

Yes your odometer is probably showing more miles than are on your truck. Try using a gear for the cable end with one more tooth than the one that you have now. See where that gets you.