Differential Options Explained


Trac Lock – The Trac Lock is a classic clutch style limited slip differential. When the unit is new the clutches provide a torque bias that applies power to both axles equally under acceleration. When the vehicle goes around a corner, the clutches provide a limited slip that allows the wheels to spin a different rates. Modern tire grip and high horsepower can easily overpower the clutch bias, and cause the unit to behave more like an open differential that a limited slip. Trac Locks require periodic maintenance as normal driving wears the clutches and reduces the bias.

Truetrac and Wavetrac - Helical gear limited slip differentials (HGLSD) are the modern replacement for the classic clutch style limited slip differential. Under normal driving conditions, HGLSDs operate as a standard or open differential, allowing one wheel to spin faster or slower as necessary without the noise or harsh operation of a clutch style limited slip. When a drive wheel begins to slip, the helical gears inside the differential automatically engage, transferring torque to both rear wheels to maximize traction. When the wheels regain traction, the differential resumes normal operation. Unlike traditional clutch type limited slip differentials, HGLSDs require no special oil additive or maintenance to replace worn and tired clutches, as these units have no wearable parts, require no special maintenance and maintain their torque bias for the life of the unit.

ARB Air Locker - Selectable locking differential, allows the driver to positively lock or unlock the differential on demand with the flick of a dash-mounted switch. As the name implies, an on-board air compressor (sold separately) is used to apply the locking force. Once locked, the differential behaves like a spool, driving both wheels equally. When unlocked the locker behaves like an open differential, driving only one wheel at a time – usually the wheel with the least traction. The key benefits of the ARB Air Locker are its predictable behavior and legendary strength.

Detroit Locker - Automatic locking differential, designed to lock and unlock automatically when torque is applied in either a forward or reverse direction, when locked it acts like a spool driving both wheels equally. When coasting or rolling into a corner (no torque applied) the Detroit Locker unlocks and momentarily operates like an open differential permitting the wheels to rotate freely. When torque is applied, exiting the corner the unit locks and drives both wheels equally. The key benefits of the Detroit Locker are its rugged construction and superb performance. The only negative is that the automatic lock and unlock operation can create a clunking sensation that can be both felt and heard in the vehicle.

Spool – The spool is the simplest and strongest option, but it lacks differential action, as both axles are joined together by the spool's solid center. Spools are not recommended for the street, as the place high twisting loads on the axles, increase tire wear and can negatively impact handling. Spools are typically only used for drag racing applications where straight line performance is the only concern.

API GL-6 Requirement

Due to the high-offset hypoid design (read very high shear) of the 9-inch ring and pinion gears, a sever duty petrolium based gear oil with API GL-6 specification is mandatory. Use of synthetic or GL-5 specification gear oils will result in premature wear of the gears and excess heat buildup that will damage internal components, voiding the Currie Warranty.