What lubrication arrangement do outboard planetary axles require?

• A. A separate oil supply for lubrication
• B. The same oil as the main differential
• C. No oil
• D. Oil supplied by the transmission

Answer: (A)

Outboard planetary axles have their own lubrication path because the planet gearset sits in a separate housing with distinct lubrication needs. The gears and bearings there operate at different speeds and temperatures than the main differential, so they require oil with the right viscosity and additives provided in a dedicated supply. Keeping this area separate also prevents cross-contamination from differential or transmission oil, helping maintain proper lubrication even if other parts of the drive train differ in condition. Using the same oil, or feeding oil from the transmission, would not reliably meet the lubrication requirements of the wheel-end planetary gears, and having no oil would lead to rapid wear.