What Causes the Impact Sound When Shifting to Reverse Gear in an Automatic Transmission?

[McBraxton]

The essence of this sound is the hard impact between the reverse gears, which occurs when shifting to reverse before the car has come to a complete stop. This causes intense wear on the gears, making them increasingly prone to gear grinding, slipping out of gear, and entering a vicious cycle, ultimately leading to major repairs. The reasons for the noise when shifting to reverse gear are as follows: 1. Reverse gear lacks a synchronizer: The synchronizer is an internal device in the transmission that ensures smooth gear engagement when shifting. If the clutch is depressed and the gear is immediately shifted, the reverse gears will collide due to speed differences, creating resistance and gear grinding noise. 2. Friction between gears during shifting: When the clutch is depressed, the reverse gears in the transmission may still be rotating for a short time. Shifting at this moment can cause gear grinding. The solution is to wait a few seconds after depressing the clutch until the rotating reverse gears have completely stopped before shifting, which will eliminate the abnormal noise. Therefore, when shifting to reverse, it is essential to ensure the car is fully stopped by pressing the brake before engaging the gear.