What Are the Differences Between Gravity Drain and Machine Flush for Transmission Fluid Replacement?

[McBethany]

The differences between gravity drain and machine flush for transmission fluid replacement are as follows: 1. Operational and Consumption Differences: Transmission fluid cannot be completely drained by gravity alone, whereas a flushing machine requires additional transmission fluid for the process. 2. Effectiveness Differences: Gravity Drain Method: The new fluid mixes with the old fluid. Machine Flush Method: Not only is the fluid replaced more thoroughly, but the flushing machine also circulates the old fluid, helping to remove metal shavings and debris trapped in the fluid passages and chambers along with the old fluid. Detailed explanations of gravity drain and machine flush methods: 1. Gravity Drain: This involves loosening the drain plug at the bottom of the transmission pan to allow the old fluid to flow out by gravity, followed by refilling with new transmission fluid. Traditional gravity drain typically leaves more residual old fluid due to the transmission's complex internal design and the shape of the transmission pan, which can hold some fluid. To further reduce the amount of old fluid, you can remove the pan by unscrewing the surrounding bolts and clean it. 2. Machine Flush: This method connects a flushing machine to replace the transmission fluid. The vehicle must be started during the process, allowing new fluid to be injected into the transmission while the old fluid is pushed out under pressure. The machine's viewing window clearly shows the transition from old to new fluid until the colors match.