Mine range from 425xxx on the F2(DE1)bodies to 460xxx + on the F2A/F2ASs. At what vintage of drive do the problems appear?
Right around the 440xxx serial range, also when Nikon switched to the often-broken black plastic tabs to hold the body in place. So, probably around the time that the MD-3 and AW-1 were introduced. The gears tend to wear out on the MD-2's with heavy use, so, with a gently used MD-2, you might not yet notice it, whereas, with a beater, it'll quack like a duck when it advances the film. When you've a chance, I'd probably send the newer drives to Sover and have him replace the gears with the brass gears. Supposedly also makes the drives quieter than new.