Is Gravity Drain or Machine Flushing Better for Automatic Transmission Fluid Change?

[EvangelineDella]

When performing maintenance on a car's transmission, the appropriate fluid change method should be selected based on the vehicle's actual condition and transmission model. There are two fluid change methods: Gravity Drain: Loosen the drain plug at the bottom of the transmission, allowing the old fluid to flow out under gravity. Once the old fluid stops draining, tighten the plug and refill with new fluid. This method is simple to perform and requires approximately 4-6 liters of new fluid, but has a low fluid replacement rate. Manual transmissions, with their simpler structure and less stringent requirements for transmission fluid, find this method more economical. Machine Flushing: The flushing machine connects to the transmission's fill and drain ports, enabling simultaneous injection of new fluid and extraction of the old-new mixed fluid until the transmission is filled with new fluid. This method achieves a high fluid replacement rate, effectively removing most of the old fluid. However, the process is more complex, consumes more fluid (typically requiring about 9-12 liters of new fluid), and incurs higher costs.