The Truetrac operates as a standard or open differential under normal driving conditions, allowing one wheel to spin faster or slower as necessary. When a wheel encounters a loss of traction or the terrain changes, the gear separation forces take effect and transfer torque to the high-traction wheel. The helical-shaped gears mesh with increasing force until wheel spin is slowed or completely stopped. When the vehicle exits the low traction situation, the differential resumes normal operation.
 
Mfg. #: 913A561
Application: Ford 8.8" 
Ring Gear Diameter: 8.8"
Carrier: All Ratios
Side Gear Spline: 31 Teeth
Model Years: 1979-Present
Bearing Cone: LM603049
Bearing Cup: LM603012