if the noise is a light clicking in overdrive, normal. loud clicking underdrive, abnormal.
you might find this review interesting:
asleep at the wheel, i fear. had pulled the pattersons off the trikes, needed 22 teeth on the rambler, tinkering with a derailleur post on the rover, 2 chainrings and various derailleurs and hangers. then came the delta interest [a rover seat fits a jouta delta very nicely, needed upgrade].
anyway, put the memory in gear and back when, thought it kinda neat to be able to tell when the overdrive was turned on by the sound.
sorry if i have led you astray.