What causes the car to roll when in N gear?
3 Answers
If the parking brake cable is loose, the car may roll, and shifting to N gear is meaningless as only P gear locks the transmission shaft. Below is additional relevant information: 1. Rolling: Refers to coasting in neutral or with the clutch disengaged. 2. Disadvantages of rolling: Coasting in N gear can damage the car. Since automatic transmission vehicles generally use pressure lubrication, where an oil pump delivers oil to areas requiring lubrication, coasting in N gear can lead to insufficient oil pressure, especially at high speeds. Inertia coasting typically occurs at high speeds when one considers utilizing it, which may prevent certain transmission components from receiving adequate lubrication, potentially causing severe damage to parts. Even at lower speeds, components still require sufficient lubrication, so coasting should be avoided in automatic transmission vehicles.
The other day I was driving on a ramp and wanted to temporarily park to grab a coffee, so I casually shifted into neutral. As a result, the car rolled down the slope and almost hit the vehicle in front, which really scared me. Since then, I've learned my lesson—shifting into neutral completely disconnects the engine power, allowing the wheels to rotate freely. At this point, the car has no braking force, and any slope will cause gravity to pull the car downward. Using neutral on flat ground is fine, but it's extremely dangerous on slopes. I recommend either shifting into park or keeping your foot on the brake every time you temporarily stop. Developing this habit can prevent major trouble. It's best not to cut corners for convenience—safety first. I've seen many beginners make this mistake, resulting in rear-end collisions with significant losses.
As someone who frequently works on cars, let me explain the situation: When in neutral gear, the transmission is in a neutral state, the power source is cut off, and the wheels are not constrained, allowing them to roll freely. It's normal for the car to slide downhill under the influence of gravity when on a slope, but it's extremely unsafe because the parking gear has an internal locking mechanism that engages the drivetrain to prevent movement. Therefore, when parking on a slope, always engage the parking gear and use the handbrake for added security. Remember, coasting in neutral may seem effortless, but it actually accelerates component wear and may lead to loss of control. Regularly inspect the brake system.
