Yeah, this is a little late, but I found that in the sherman, the 3:1 gearboxes provides a scale speed that's much closer to the real thing. I did quite a bit of experimentation and timing with different gearboxes and with the 3:1 I was getting a scale speed of about 28 mph. With the 4:1 it was closer to 20 mph, a little bit slow for a sherman. I still haven't tried the new V3 gearboxes, the ones with the plastic covers, but I don't really like those boxes anyway. Too noisy.