Does Shifting to Neutral at a Red Light Harm an Automatic Transmission Car?

[StMaci]

Shifting to neutral (N) at a red light does not harm an automatic transmission car. The N gear disconnects the power transmission between the engine and the transmission, while the handbrake is used to prevent rolling and potential collisions. If the red light duration is short, using N gear along with the foot brake is acceptable. However, for longer waits, it is advisable to engage the handbrake. Using D gear and the foot brake while waiting at a red light is not recommended, as the D gear maintains continuous power output, which can cause the transmission to heat up and increase wear. Similarly, using P gear to wait at traffic lights is also undesirable, as engaging P gear locks the transmission gears. In the event of a rear-end collision, this could directly damage the transmission. The transmission is a mechanism designed to alter the speed and torque from the engine, and it can fix or change the gear ratio between the output and input shafts.

[AngelaDella]

Last time I drove my dad's old Accord and stopped at a red light, I habitually shifted to N gear, and he lectured me all the way. The mechanic actually explained this: there's really no need to shift to N gear for short stops at red lights. When an automatic transmission is in N gear, the hydraulic oil pump does keep working to lubricate, but frequent gear shifts actually accelerate wear on the shift mechanism. What's most damaging to the car is staying in D gear and pressing the brake for long periods, as the torque converter remains strained, causing the transmission oil temperature to soar to 110°C. I later timed it specifically—for red lights under 30 seconds, just pressing the brake is fine. For red lights over a minute or in traffic jams, shifting to N gear + handbrake gives the transmission a breather, and I measured a fuel consumption drop of 0.2L.

[AlyssaMarie]

A colleague's newly purchased hybrid Corolla became a joke. At every red light, they would clunk into N gear, resulting in a transmission repair within three months. Nowadays, automatic cars commonly feature an electronic parking brake linkage design. When auto hold is activated by pressing the brake pedal deeply in D gear, the planetary gear set completely disconnects the power, making it even more convenient than shifting to N gear. Especially for cars with start-stop functionality, there's no need to shift to N gear when the engine has already shut down. However, for older models, be cautious: when running the air conditioning in summer and holding the brake pedal in D gear, the violent rotation of the radiator fan can cause noticeable steering wheel vibration. In such cases, shifting to N gear actually provides more stability.

[VonSilas]

When teaching automatic transmission at the driving school, the instructor emphasized: Don't shift to P when waiting at a red light! A rear-end collision could directly damage the transmission. Now when driving my CVT model, I handle traffic lights differently based on the situation: For short lights under 10 seconds, I stay in D with brakes on; at inclined intersections, I shift to N and engage the electric parking brake; for long red lights over 2 minutes, I turn off the engine. Observing ride-hailing drivers, they shift to N but keep the foot brake on at lights, claiming it prevents rolling and allows quick starts. Personally, I believe the key is minimizing gear shifts – my XR-V's shift lever bushing wore out in just three years.

[McJulianna]

Auto repair shops have seen too many AT transmission repair cases. The torque converter is in a semi-linked state when braking in D gear, which can generate metal debris over time and contaminate the transmission fluid. However, frequently shifting to N gear is worse: each shift impacts the valve body oil pressure by approximately 0.8MPa, equivalent to an additional 60 wear cycles per hour. This is especially true for models with paddle shifters—when shifting from N to D at a stoplight, the clutch must re-engage. The correct approach is to follow the manual, such as Honda's recommendation to use N gear only for stops lasting 30 seconds or longer.

[LaStella]

My cousin who has run a repair shop for ten years shared a little-known fact: When a car with auto start-stop is in D gear with the brake pedal firmly pressed, the driveshaft is actually physically disconnected. I tested this on our company's Audi A4L, and found that the transmission oil temperature was 7°C lower when the auto start-stop was active compared to being in N gear. However, older cars require caution: my 2006 Buick LaCrosse would vibrate at the steering gear when idling in N gear, and the mechanic said it was due to worn engine mounts. Driving a new energy vehicle is even simpler now—just press the brake pedal firmly to activate autohold, and since the motor isn’t running, there’s no need to worry about which gear to use.