I've been slowly putting together a basket case Legacy Atlantic, and I finally got the last piece of the puzzle, the unavailable motor. So, I put it all together and everything worked and it runs fine. However, I notice one anomaly which I can't explain. It only has two chuff/rev!
The only thing that comes to mind is the replacement Atlantic motor came from an old Atlantic, and it could have a different worm. Is it possible that a dual-start worm would work seamlessly on the existing worm gear? That would explain the two chuffs as the gear ratio would be half what a single start worm would have. It would also explain why it seems that the speed first step seems a little faster than most Legacy locomotives.
Is there any other way this could happen? The RCMC is the original board, so that isn't the issue, and that's where the chuff comes from. I did have to replace the encoder board and toothed flywheel on the motor, but I'm pretty sure all of them are the same design with the same number of pulses/rev.