This loco is only a little over a month old, and has relatively little run time. This problem did not exist at all until the last week. Ran great up until then. When it switches into "slow mode", it simply doesn't SOUND mechanical. No unusual noise, except a nearly inaudible growl, and runs perfectly. Best slow speed you ever saw, at HALF THROTTLE! Sounds like the old days when power packs had "pulse power" for slow speed.