What are typical signs that a gearbox is low on lubrication?

• A. Increased oil level
• B. No signs
• C. Increased noise and heat, and low oil level or visible leaks.
• D. Decreased noise and cooler operation

Answer: (C)

When a gearbox is running low on lubrication, friction between gears and bearings increases, which raises both wear and operating temperature. This combination often shows up as louder gear noise and hotter operation, along with signs that the oil level is dropping or that leaks are present. That combination—more noise, more heat, and evidence of reduced lubrication like a low oil level or visible leaks—is the clearest indicator that lubrication is insufficient.

The other possibilities don’t fit: having more oil would not cause the symptoms of low lubrication; no signs would miss the physical changes happening inside the gearbox; and cooler operation with less noise would suggest the opposite of low lubrication, indicating the system is well-lubricated or over-lubricated.