HP 3800 is making a groaning, growling noise only during calibration. When printing the noise is not present. Has new fuser, tranfer assy, all toner units. The lever locks are good and the cams and gears are in time. If i cheat the door interlock and disengage the transfer assy during calibration the noise stops. I have quite a few 3800's in the field and this is the only one that makes this noise. It is like the drums and transfer assy are somehow not matching speeds during calibration. Anyone seen this and know the solution? Any help would be greatly appreciated.