Which lubrication methods are used for the gearbox?

• A. Lubrication by air
• B. Splash and pressure jet
• C. Oil bath
• D. Grease only

Answer: (B)

Gearbox lubrication relies on an oil film to prevent metal-to-metal contact and to carry away heat. The two common methods that cover a wide range of operating conditions are splash lubrication and pressure jet lubrication. In splash lubrication, the moving gears dip into an oil reservoir and fling lubricant onto gear teeth and bearings, which is simple and effective at moderate speeds. In pressure jet lubrication, an oil pump delivers a focused stream to critical surfaces, providing reliable lubrication even under higher loads and speeds and helping with cooling. Air lubrication wouldn’t provide a liquid film, so it can’t properly lubricate gear teeth. An oil bath is another possible method, but the combination of splash and pressure jet is the typical approach described. Grease-only lubrication often can’t meet cooling and film requirements for many gearboxes.