What is the reason for the loud noise in M gear?

[JustinLee]

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.

[DelTeagan]

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.

[SanVictoria]

When I drive my car in M mode, the sound is always much louder than in automatic mode. I believe the main reason is that manual operation makes me habitually maintain low gear at high speeds, such as when overtaking or climbing hills, forcing the engine to operate at higher RPMs, which naturally makes the sound louder. Additionally, the more intense fuel combustion at high RPMs, combined with accelerated exhaust flow, increases the overall noise. In my experience, this isn't necessarily bad; it often just indicates that the engine is working more efficiently. However, if the sound suddenly becomes harsh or is accompanied by unusual noises, it's time to check for transmission issues or aging spark plugs. To reduce noise, I make sure to shift up in time on flat roads to ensure a smoother ride.

[Tiffany]

Driving in manual mode feels exhilarating when the engine roars, because I can intentionally keep the engine at low gear and high RPM. In this state, combustion inside the cylinders accelerates, and the exhaust emits a more intense sound, making it louder. Many cars are tuned to amplify the exhaust note in sport mode, enhancing the interactive experience. As the RPM increases, the sound naturally intensifies, representing strong power output. If there are abnormal noises like rattling, it might require maintenance.

[LaVincent]

When driving in manual M mode, I noticed increased noise primarily because direct gear control allows the engine to operate across a wider RPM range. At higher RPMs, cylinder pressure rises, intensifying combustion noise, while the exhaust system resonates more strongly. This is typically not a malfunction but by design to enhance driving feedback. However, if the sound includes metallic scraping or fluctuates significantly, it may indicate transmission adjustment or cooling issues. Understanding normal engine sound variations can help ensure peace of mind.

[DelCourtney]

During M mode driving, increased engine noise is a common phenomenon, as I typically push higher RPMs to obtain more torque, especially during rapid acceleration or mountain road driving. Lower gear operation causes the engine to rotate quickly, generating loud noises. Exhaust heat flow under load creates greater sound, which mostly reflects the vehicle's performance. However, if the noise persists with a hissing sound or abnormal vibrations, it is advisable to check the transmission fluid or engine gaskets to avoid potential wear. Proper maintenance, such as oil changes, can help control noise levels and ensure driving safety.