Which fluids should be regularly checked for proper truck maintenance?

Regularly checking transmission fluid and brake fluid is crucial for maintaining a truck's performance and safety. Transmission fluid ensures the proper functioning of the transmission system, facilitating smooth gear shifts and preventing overheating. Insufficient or contaminated transmission fluid can lead to transmission failure, causing significant damage and costly repairs.

Brake fluid is equally important, as it is essential for the braking system's effectiveness. If the brake fluid is low or degraded, it can lead to diminished braking performance or even complete brake failure, putting the driver's safety at serious risk. Maintaining the proper level and quality of brake fluid is essential for ensuring that the brakes respond reliably in various driving conditions.

While the other options include fluids that are important for vehicle maintenance, they don't encompass the critical systems represented in the correct answer. For instance, while engine oil is vital, it does not go hand-in-hand with battery fluid checks, which are less frequently required. Coolant is important for engine temperature management, but it does not correlate with air filter fluid, as air filters generally do not utilize a fluid. Finally, while windshield washer fluid is necessary for visibility, it does not match the importance or critical safety implications of transmission fluid and brake fluid in truck maintenance.