What is the reason for the loud noise in M gear?
2 Answers
m gear loud noise is caused by the vehicle speed being too slow while the gear is too low, resulting in excessively high engine RPM. There are three key points regarding gear selection in automatic transmission vehicles: 1. When encountering a red light: You can temporarily stop and hold the brake in D gear without harming the vehicle, as the torque converter in the transmission is equipped with a reaction wheel with a one-way clutch that amplifies torque from the engine crankshaft. It does not rotate at engine idle speed and only engages when the engine RPM increases; 2. During driving: The driver can freely switch between forward gears. Although the gear limits the highest achievable gear, as long as the gear matches the speed, free switching is possible; 3. When starting the vehicle: The brake pedal must be depressed to move the gearshift from P or N gear into a driving gear. Releasing the brake pedal allows the vehicle to move slowly. The purpose of pressing the brake in advance is to ensure the safety of both the driver and the vehicle.
When I switch to manual M mode, the engine sound becomes noticeably louder, primarily because in this mode, I actively keep the engine operating in the higher RPM range for extended periods. For example, during acceleration or climbing hills, I might stay in second or third gear without upshifting, causing the engine to rev higher with more intense combustion, naturally producing more noise. At the same time, the exhaust system resonates more strongly under such high loads, amplifying the sound. I find this not only normal but also a reflection of the vehicle's responsiveness; many sport-oriented cars deliberately enhance this exhaust note to increase driving pleasure. However, if the sound resembles metal clanking or persistent abnormal noises, it's time to check the transmission or engine oil. In daily driving, paying attention to engine health can prevent major issues—for instance, changing the oil early can help reduce unusual noises.
