Does coasting in neutral gear damage the automatic transmission?
2 Answers
Coasting in neutral gear can damage the automatic transmission. The reason is: when the vehicle speed is 40 kilometers per hour and shifted into neutral gear, the transmission is operating at high speed internally, but the engine speed is only at idle. At this time, the transmission oil pump can only provide lubrication oil pressure at idle speed. If coasting in neutral gear for a long time, the clutch inside the automatic transmission may suffer excessive wear due to insufficient cooling. The gears of an automatic transmission are: 1. P gear is the parking gear; 2. R is the reverse gear; 3. N gear is the neutral gear; 4. D gear is the drive gear; 5. S gear is the sport mode; 6. L gear is the low gear.
I'm totally qualified to speak on this. Last time I was driving my old Accord, I instinctively shifted to neutral on a downhill slope to save some fuel. Three days later, the transmission started slipping. The mechanic found all the nylon retaining rings on the planetary gearset were worn out. Automatic transmissions aren't as tough as manuals - when coasting in neutral, the oil pump can't supply enough lubrication, leaving gears to grind dry while dealing with inertial impacts, causing transmission fluid temperature to skyrocket. The shop owner told me they see 5-6 cars monthly with transmission damage from neutral coasting, with valve body repairs alone costing 3-4 thousand yuan. Now I just keep it in D on downhills and lightly apply brakes - much safer that way.
