When servicing a rear differential with limited slip, the technician should

• A. Use standard gear oil
• B. Use a special additive
• C. Reuse existing oil without changes
• D. Avoid additive entirely

Answer: (B)

Limited-slip differentials rely on friction modifiers in the gear oil to control how the clutch or friction surfaces engage. When servicing, you need a gear oil that includes the proper friction characteristics, or you must add the manufacturer-recommended friction-modifier additive. This helps the differential engage smoothly, reduces chatter, and protects gears and bearings. Without this additive, standard gear oil may not provide the required friction properties, leading to poor LSD performance, noise, and premature wear. So the correct approach is to use a special additive in the lubrication as specified.