I don't remember, but it was fairly easy. Someone posted how to do this on the old BB.com message board a few years ago. However, it's like riding a bike. I'm sure that I could figure it out once I do it.

From what I remember, there are lock springs between each set of number rolls. There is little room to move each roll sideways, I believe from the right side, since the odo works from the right to the left. Once you move each roll to the side, the spring lock is unlocked, allowing full rotation of the number roll. After you're done rolling the particular roll, you'd just snap it back in place, thus locking it. You'd want to do this procedure for each consecutive number roll. However, you'd have to pull out the number rolls together after you've done each one all the way to the last one.

This works for 48-52 and likely for other years as the odometer was the same in design. I'll try to put together a "how-to" article.

On your speedometer, there might be some broken gears on the odometer or a loose connection. As with anything on these trucks, the speedo assembly is fairly simple. It's easy to take apart and reassemble.

 

Thanks Ilya for the information and a how to article would be useful. I know they are fairly basic as I've partially disassembled the extra one I have, yet I was unable to figure out how to roll the number back but it doesn't matter because the dang thing doesn't work anyway. It appears as though the shaft that connects to the speedo cable is binding and won't spin freely, but as to why I don't know. The other one with the non working odometer I took it apart but failed to see what the problem was. Any ideas?