Which gear should an automatic transmission car use when going up and down long slopes?

[CalvinLynn]

The correct practice for an automatic transmission car going down a long slope is to shift from D gear to a low gear. Some automatic transmissions have an L gear, which stands for Low gear, designed for safety considerations. When descending a long slope, the L gear can utilize the engine's resistance to control the vehicle's speed, reducing the frequency of using the car's brakes and preventing the danger caused by brake fade due to frequent braking. Below are specific details about automatic transmission cars going downhill: 1. If encountering a short slope, you can simply stay in D gear and apply the brakes to pass. However, for long and steep slopes, keeping the automatic transmission in D gear and continuously applying the brakes can easily cause the brake discs to overheat, reducing braking performance and significantly diminishing the braking effect. Therefore, it's best to avoid this practice. 2. Nowadays, many models come with an M gear, which stands for Manual mode. By switching to manual mode and then shifting to 1st or 2nd gear, you can utilize the engine's low-gear braking effect, combined with intermittent braking, to control the vehicle's speed.

[SanAubrey]

When driving an automatic transmission car on long slopes, I'm used to shifting gears in advance. On long downhill slopes, you should never keep pressing the brakes—those things can easily overheat and fail. Instead, shift to L (Low) or M (Manual) mode to use engine braking to control speed, just like downshifting in a manual transmission to save brake pads. Before climbing a steep slope, don’t foolishly wait for the car to downshift on its own; switch to S (Sport) or manual mode in advance to lock in a lower gear. This gives more power for climbing and prevents the transmission from frantically shifting like it's having a seizure. Once, I drove a friend’s car on a winding mountain road with a continuous 7-8 km downhill stretch using only L mode—the brake discs weren’t even hot to the touch afterward.

[DeAdelyn]

I've figured out that the principle of automatic transmission climbing hills is mainly about downshifting to increase torque. When going down a long slope, you should actively switch to the restricted gears, such as '1', '2', or the gear marked with a slope symbol. At this time, you can clearly feel the vehicle speed being dragged by the engine braking. If you feel the car lacks power when going uphill, just pull the gear lever to switch to sport mode, and the engine roar will make the climb more exciting. My car with paddle shifters is even more convenient—just flick the paddle to downshift two gears when going downhill, and even the central control screen displays the engine braking power bar.

[DeMaya]

Novice drivers of automatic cars are easily misled by the idea of 'using D gear for everything.' When climbing a steep slope and noticing the RPM fluctuating, it's time to shift gears. Press the gear lever unlock button and push it to the left into the manual zone—displaying '1' or '2' on the dashboard is the safest. Never rely solely on brakes when going downhill. Last year, there was a report about a driver who used D gear continuously for ten kilometers downhill, causing the brake pads to emit blue smoke. When teaching my wife to drive, I specifically demonstrated: on the same route, using D gear downhill required over twenty brake presses, while switching to L gear needed only three light taps.

[LeJoanna]

When encountering a long downhill with hairpin turns, I usually do this: before entering the slope, shift the gear lever from D to L. At this point, the RPM will suddenly surge to 3000, but don't panic—the speed is immediately controlled by engine braking. That time when driving a pickup truck on a mining road, a vehicle in the same convoy that didn't engage low gear had its brake fluid boil. If driving a small-displacement car uphill, extra caution is needed. Last time when driving a 1.5L car uphill, it just roared in D gear without moving, but switching to manual 1st gear made it much steadier. A mechanic told me that cars frequently using D gear downhill experience brake disc wear three times faster than normal.

[JustinFitz]

While researching transmission fluid temperatures, I discovered a critical point: continuous downhill driving in D mode causes the transmission to repeatedly shift up and down, raising fluid temperature by 20°C compared to using fixed gears. So now when encountering mountain roads, I directly lock into 2nd or 3rd gear downhill - similar to how heavy vehicles use hydraulic retarders. Uphill driving requires even more attention to avoid frequent gear hunting; vehicles using paddle shifters to downshift in advance show noticeably quicker throttle response. A tuning shop owner taught me a trick: during long descents, watch the tachometer and maintain a gear that keeps RPM around 3,000 for optimal safety. Once in the Qinling Mountains using this method, I completed a 7km descent without ever touching the brake pedal.