The Blackline limited slip differential for the Ford Mustang and Ford USA applications with a 9-inch Ford axle featuring 31 splines, also known as an LSD (limited slip differential), improves traction by distributing torque between the two-wheel drive drive wheels based on available grip.
Its helical gear design allows the limited slip differential to transmit more torque to the wheel with the best traction. As torque increases, the gears exert pressure against the differential housing and generate the internal friction necessary for this torque distribution. The system thus allows for better utilization of available traction, particularly during hard acceleration and when exiting corners.
Under light loads, the helical limited slip differential maintains smooth, progressive, and quiet operation. The wheels can continue to rotate at different speeds when necessary, particularly when cornering. This feature enhances traction during spirited driving while maintaining handling suitable for on-road use.
The Blackline limited slip differential uses a parallel-shaft helical gear architecture optimized to distribute forces. Its 5:1 torque split means that when one of the wheels loses traction, the wheel with the most traction can receive up to five times the torque transmitted to the spinning wheel.
As with any helical-gear limited slip differential, a minimum amount of resistance must remain on the wheel with the least grip to allow torque transfer. It is therefore most effective when both wheels maintain a minimum level of traction.
The Blackline HLF017/31 limited slip differential is designed for Ford USA vehicles equipped with a Ford 9-inch rear axle with 31-spline driveshafts. This may include certain Ford Mustang, Fairlane, F-Series, Thunderbird, Bronco, Torino, and Ranchero models, depending on the year and configuration. It is essential to verify the axle type and the number of splines before ordering. Its housing and gears are made of high-resistance 8620 steel.
Manufacturer Part Number: HLF017/31
Quaife application match: QDH1R
Type: Helical-gear limited slip differential
Vehicle compatibility: Ford Mustang (1964–1973), depending on configuration
Vehicle compatibility: Ford Fairlane, depending on configuration
Vehicle compatibility: Ford F100 / F150, depending on configuration
Vehicle compatibility: Ford Thunderbird, depending on configuration
Vehicle compatibility: Ford Bronco, depending on configuration
Vehicle compatibility: Ford Torino and Ranchero, depending on configuration
Type of axle: Ford 9-inch rear axle
Grooves: 31
Torque split ratio: 5:1
Housing and gear material: High-resistance 8620 steel
Mounting: Direct replacement for the original differential on compatible vehicles
