Okay,

So I am starting to organize the srop of my 1985 D150. I am trying to account for an alternate tire size. 225/60-15 seems like a decent choice, however, it changed the speedometer by more than 10% over the stock 225/75-15 what can be done to mitigate this problem? Is there a gear to change?

Thanks!!~~Heath

 

These folks have speedo gears; http://www.transmissioncenter.net/dodge.htm
Just scroll down to find them, not sure if they have yours, you might need to call them.

 

I ran into a similar problem when I put a different transmission and different tires/wheels on a '70 Ranchero. Never did have much luck finding out the part numbers for the gears from Ford but I found some info online through Mustang places. Eventually found a Ford part number vs. number of teeth on the driven gear. They called the main gear in the tranny the drive gear and the small gear on the end of the speedo cable the driven gear. Each additional tooth on the driven gear changed the speedo reading a certain percent. I took the numbers into Ford and they were only $7 or so for the gears...took me two tries but eventually I got it so my speedo was withing a few percent. I'm guessing Dodge has a similar setup.

Derek