On preflight, the oil level of the main transmission is checked via the ______ ______.

• A. Oil gauge
• B. Pressure sensor
• C. Sight glass
• D. Fluid dipstick

Answer: (C)

The correct choice is the sight glass because it allows for a visual inspection of the oil level in the main transmission. A sight glass is a transparent window or tube that shows the fluid level through direct observation. This method facilitates quick checks without the need for special tools or procedures, ensuring that operators can easily ensure that the oil level is within the appropriate range for safe and efficient operation.

The other choices do not serve the same purpose effectively. An oil gauge typically indicates pressure rather than level, a pressure sensor measures the pressure of the fluid but not its level, and a fluid dipstick is not typically associated with transmission oil checks in many lifting systems, as the level needs to be assessed in a way that allows for viewing without removing components. These alternatives may serve different functions but do not specifically enable direct visual assessment of the oil level in the main transmission.