The PowerTrax GRIP LOK is the latest design in traction adding differential technology. It combines the fully automatic locking action of our traditional locker, with the strength of a fully machined case. Using our automatic locking technology, the PowerTrax GRIP LOK delivers automatic mechanically actuated traction. This is our strongest locking differential, offering the ultimate in competition and off-road capabilities. The PowerTrax GRIP LOK comes fully assembled. Always use 80W-90 weight petroleum based gear oil with a GL-5 (or higher) rating, friction additive/modifiers should NOT BE USED. Synthetic oils and oils containing friction modifiers are not recommended. Designed for rugged competition and off-road traction needs, this is not for the timid! POWERTRAX EXTREME TRACTION SYSTEMS are the ideal solution for just about any light truck, sport utility, and muscle car on the road today. Whether you need the safety of added traction for daily commuting, recreation, work, or just so your muscle car puts power to the pavement instead of burning one wheel up, the POWERTRAX EXTREME TRACTION SYSTEMS are your answer.