Why Shouldn't You Coast in Neutral Downhill?

[AnthonyFitz]

Here are the reasons why coasting in neutral downhill is not advisable: 1. When coasting in neutral, the engine stops running, causing the air compressor to cease operation. Since the vehicle requires frequent braking, the compressed air in the air reservoir continuously depletes, which may lead to brake failure. 2. It can easily damage the transmission. The transmission primarily uses rolling bearings. While coasting in neutral, the second shaft of the transmission rotates, but the constant-mesh gears remain stationary. As a result, these gears cannot agitate the gear oil in the transmission, and the bearings (especially those positioned higher and relying on splash lubrication) do not receive adequate lubrication, leading to premature wear of the bearings and gears. 3. Some drivers, aiming to save fuel, depress the clutch and turn off the engine to coast downhill. When they suddenly release the clutch pedal at the bottom of the hill to restart the engine, power is transmitted in reverse. The transmission path is: drive wheels → half shafts → differential → final drive → driveshaft → second shaft of the transmission → synchronizer → clutch. Since the clutch abruptly engages with the stationary flywheel, it endures significant impact loads, which can easily damage the clutch friction plates.