Rolling forward in reverse gear (R) can cause significant harm to an automatic transmission. When an automatic transmission vehicle rolls forward without being shifted into R gear, it generally does not affect the transmission because the vehicle is in neutral (N) or drive (D) position, which are normal gear settings. However, if the vehicle is shifted into R gear while still moving forward, causing it to roll, this action can increase wear on the transmission and potentially lead to gear grinding, which is a highly dangerous practice. Below is relevant information: Precautions for Automatic Transmission Roll: If an automatic transmission vehicle rolls backward during hill starts, it is likely due to insufficient idle speed when only in D gear without applying throttle. This can cause the engine to stall, as it cannot provide enough power to start the vehicle on a slope. Once rolling occurs, it becomes even more difficult to avoid stalling, as the engine must not only provide mechanical energy for starting but also counteract the kinetic energy from rolling backward. In such cases, the driver must first press the brake and clutch to stop the vehicle completely before restarting. Automatic Transmission Power Delay: After releasing the pedal, automatic transmission vehicles experience a power delay of about one second, which is more pronounced in dual-clutch transmission models. When starting an automatic vehicle, releasing the brake triggers this power delay, which can be long enough for the vehicle to roll backward.
