Snap: 1546 Metal knocking sound underframe when moving. ~~~~~ Snap: 1546 Metal knocking sound underframe when moving. CE checked : 1546 bogie 2 knocking sound suspect came from centre pivot (compound spring).  1546 bogie 1 & 2 checked/found no abnormalities. WN coupling, spring pressing device, vertical/horizontal shock absorbers, centre pivot lateral stop, car height, axle bump stop, coil spring rubber arm, gangway height & wheel condition - All checked - OK. OPS 20 raised to follow-up.  Aliff/Daniel/Redzwan/Chan SW 45329 To follow up.  1546 Checked gangway tilt and gap differential ok. Due to measurement of center pivot out of criteria & adjusted carbody height to minimum acceptance level. #1546 Unable to duplicate in depot. Measured center pivot vertical stop V1 and V2 ok after rectification. Depot shunting no knocking noise.  Lee PT/Alan/Anand/Sugu 45329