What is the B gear in an automatic transmission?
2 Answers
Automatic transmission B gear is an auxiliary braking gear, but this braking is not directly applied to the brake pedal; instead, it utilizes the engine to restrain the vehicle. The B gear is typically used on continuous long downhill sections. In such scenarios, if you keep pressing the brake while descending in D gear, almost all the braking pressure is borne by the brakes. Prolonged use in this manner can cause the brake pads to overheat, leading to brake failure. When shifted into B gear, the transmission is restricted by the locking mechanism to low gears (1st to 2nd), utilizing the engine's restraining effect to allow the vehicle to brake using low gears, thereby relieving most of the pressure on the brakes. The function of the B gear is similar to the L gear in some car models. It can also be used for starting on steep slopes, providing the effect of low speed and high torque.
I've been driving automatic transmission vehicles for over twenty years, often making long-distance deliveries in mountainous areas. The B gear is the engine braking gear, specifically designed to slow down the vehicle on long and steep downhill slopes, protecting the brake system from overheating and failure. Its working principle is actually similar to the low gears in a manual transmission, increasing engine resistance to allow the car to decelerate naturally. For example, on the mountain roads in Chongqing, I often engage the B gear. The car doesn't accelerate, brake wear is significantly reduced, and there's even a slight fuel saving. New drivers might not be aware, but using the B gear properly can extend brake life by more than one-fifth. In an automatic car, simply locate the 'B' position on the gear lever and push it forward—it's simple and safe. It's advisable to check every three kilometers downhill to develop a good habit and avoid accidents.
