Detroit Locker for Dana Spicer 70-HD differential with 35 spline axles. For 4.56 and up, add .125 for non-HD. The Detroit Locker provides maximum traction for off-road or racing use. The heavy-duty case and internals provide a dramatic increase in strength while giving 100% torque to both tires. The mechanically-operated unit works by locking while under power and unlocking when you let off the gas, allowing you to turn. Unit comes standard with a one year warranty against workmanship defects.