2200 making a clicking noise

[twisted8]

i was doing some routine maintenance on my truck and i had to re center my servo so i plugged in two packs and fired up the truck. (no pinion). i centered the steering servo and for the heck of it i hit the throttle and i heard a clicking coming from the motor. it only does it on initial input to the throttle.not while it has constant throttle input and its only one click.

motor didnt get hot last time it was ran and its never been over 120-130.

any idea what this is ?

mmm, 2200 combo with latest firmware.