300D vs 280 (gasser) odometer gears...

[jesserobot]

So finally got around to replacing the ignition switch on my 85 300D. Decided while i have the instrument cluster out I should look into fixing the broken odometer and the instrument cluster housing. The odometer and trip hasn't worked for a few+ miles so it was about time.

I went to the local pullapart and found a nice instrument cluster intact in a 83' 280. The housing was the same so for $12 I figured it would be worth it to see if the odometer worked. It had roughly the same about of miles (minus the ones since mine stopped working ).

Switched out the housing and the speedo/odometer and hooked everything back together and viola! The odometer worked! But now the problem is that it is not calibrated the same as the old odometer. The speedometer reads slower and the odometer records less miles.

My question is... do I just need to switch some of the gear(s) out of my old speedo and put it in the new one or... is there some kind of calibration that needs to be done (and is it easy to do)? And which gear(s) need to be switched if that is what needs to be done. Anyone ever dealt with this issue???