What to do if you hear a gearbox wailing or growling
If a growling sound is produced during the gear change, it is likely that the clutch needs adjustment – it doesn’t fully disconnect the engine from the transmission. Growling that appears when a specific gear is shifted means the synchromesh is busted – in which case it is preferred that the gearbox is repaired in full.
Automatic transmission enriches the car’s vocal range with a good dozen of “philological delicacies”. The sound of the wailing siren – nearby and not too loud – means the torque converter sends its best regards. However, if this sound appears shortly during the stall speed test and disappears afterwards – then there’s no need to worry.
Constant howling sound from the gearbox of a stationary vehicle, surging or fading depending on the engine’s rpm, may indicate the low gearbox oil level. Aside from that, there might be air bubbles in the oil pump due to wear of ring and sealing gaskets; there may be a damage or a wear to oil pump gears; the gears might have been incorrectly housed into the oil pump body during assembly; or the gears of the pump are meshed improperly.
The buzzing sound indicates the vibration of line oil pressure control valve spool or the play of some torn or worn out packing gland. The volume also depends on the engine speeds.
Constant rattling sound at low engine speeds means the breakdown of the pump, turbine wheel blades or damper springs in torque converter is possible.
Intermittent rattling sound in a moving vehicle at low engine speeds (the sound may disappear for a short period during shifting the gear lever to N or P positions) points at the engine flywheel likely being damaged.
If an unusual sound appears when a specific gear is shifted and disappears when the gear is changed, then it probably means that one of the planetary gear sets of the given gear is defective. If this sound does not disappear but merely its tone changes when other gears are shifted, then block bearings or bushings are worn out. Did you memorize it? No? And there’s no need to!
All you need to know is, the fully operational automatic transmission does not produce any sounds. Should those appear – it would be wise to visit the service station for a check. Especially if you plan a trip away from home or civilization.