What happens if too much manual transmission fluid is added?

[LeAustin]

Excessive manual transmission fluid can lead to high oil pressure, which may cause oil seal leaks. Additionally, the excess fluid can overflow through the vent hole, increasing internal gear resistance. The following are expanded scenarios of overfilling manual transmission fluid: 1. Clutch damage: When the fluid exceeds the dipstick line and submerges the gears, starting the car requires the gears to overcome the fluid's resistance, resulting in power loss. Moreover, the agitation of the gears can cause the fluid to foam, introducing air into the oil passages and reaching the clutch. When shifting into D gear, air trapped between the clutch plates prevents proper engagement, leading to clutch slippage, inability to move the car, and accelerated clutch wear. 2. Reduced transmission efficiency: The primary functions of transmission fluid are lubrication and cooling. The fluid transfers heat to the transmission housing and cooler for dissipation. Overfilling increases gear rotational resistance, impairing the transmission's cooling capability and power transfer efficiency, thereby requiring the engine to consume more fuel and reducing overall fuel economy. 3. Increased transmission temperature: Most of this energy loss is converted into heat within the transmission, causing a continuous rise in temperature. This eventually leads to premature bearing wear and friction plate damage, both of which are costly to repair or replace. In conclusion, neither overfilling nor underfilling is advisable. Transmission designs undergo rigorous lubrication and temperature rise testing, with fluid levels precisely calibrated.