What are the implications of using an incorrect gear oil viscosity in a limited-slip differential?

Using an incorrect gear oil viscosity in a limited-slip differential can lead to several problems, including reduced performance, increased wear, and potential damage to the differential. Limited-slip differentials rely on friction modifiers in the gear oil to allow the clutch packs or cones to slip smoothly when needed, while still providing sufficient friction to limit wheel spin. Viscosity is a measure of a fluid's resistance to flow. If the gear oil viscosity is too low, it may not provide adequate lubrication to the gears and bearings within the differential, leading to increased wear and potential failure. A low-viscosity oil may also not properly suspend the friction modifiers, reducing their effectiveness. Conversely, if the gear oil viscosity is too high, it can prevent the clutch packs or cones from engaging and disengaging smoothly. This can lead to excessive chatter or binding, reducing the differential's ability to differentiate wheel speeds during cornering. A high-viscosity oil may also increase the internal friction within the differential, leading to higher operating temperatures and reduced efficiency. Incorrect viscosity can also affect the performance of the friction modifiers. If the oil is too thick, the friction modifiers may not be able to properly reach the friction surfaces. If it is too thin, the friction modifiers might not be effective at controlling the friction. For example, using a standard GL-5 gear oil in a limited-slip differential that requires a GL-5 oil with limited-slip additives can cause the differential to chatter and bind during turns. Similarly, using an 80W-90 gear oil in a differential designed for 75W-90 can lead to increased operating temperatures and reduced efficiency.