Speedmaster Third Member Assembly HD Case 31-Spline TorqueWorm LSD Ford 9”
Highlights
- A356-T6 Aluminum Construction
- 6-Pinion Gear Differential
- Reduces Internal Load Stress
- Heat-Treated For Durability
Speedmaster Ford 9” HD Case Third Member Assembly with 31-Spline TorqueWorm LSD.
The Speedmaster Ford 9" HD Case Third Member Assembly with 31-Spline TorqueWorm LSD is an exceptional product suited for daily drivers, street rods, and race cars alike. The A356-T6 aluminum construction, one-piece billet bearing caps with through-bolt center section design, and 12-point through bolts make this third-member assembly incredibly strong, with a horsepower rating of over +1,000. The unique TorqueWorm 6-pinion gear type limited-slip differential is preloaded and faster-reacting, with stress spread over a greater surface area to reduce internal load.
Features and Benefits:
- Great for daily drivers, street rods, and race cars
- A356-T6 aluminum construction
- One-piece billet bearing caps with through-bolt center section design
- +1,000 horsepower rated
- Includes 12-point through bolts and billet pinion support
- Unique TorqueWorm 6-pinion gear type limited-slip differential
- Preloaded and faster-reacting unit
- Spreads stress over a greater surface area to reduce internal load
- EN36 material is made for racing applications
- 8620 chrome-nickel-Moly steel outer case for long life and strength
- CNC machined high-quality gear sets
- Heat-treated for extreme durability and high impact
- Lapped for correct tooth contact and smoothness
- TDS long-style billet yokes CNC machined to exact specifications
- Available in several gear ratios
Made with EN36 racing material and featuring a CNC machined high-quality gear set that is heat-treated for extreme durability and high impact, this assembly provides long-lasting performance upgrades. The assembly is also lapped for correct tooth contact and smoothness. Available in several gear ratios, this third-member assembly is a serious contender for any automotive application requiring top-level performance and reliability.
Specifications:
- Part type: third member complete assembly
- Product line: standard-nose case
- Case style: Ford 9”
- Case material: aluminum
- Main cap material: aluminum
- Main cap retention style: thru-bolt
- Carrier bearing diameter (in): 3.250”
- Pinion support bolt quantity: 10
- Standard pinion location: yes
- Ring gear load bolt: no
- Ring and pinion included: yes
- Yoke included: yes
- Yoke style: 1350 series
- Bearings included: yes
- Carrier type: 31-Spline Speedmaster Torque Worm LSD
Vehicle Fitment:
- 1965-1973 Mustangs
- 1948-1979 F-100s
- 1966-1977 Broncos
Please Note: These 3rd members are to be used with a mineral-based oil of a range of EP140 Extreme pressure at a minimum. NO split grades such as 85/140 (these are not recommended). Failure to use the correct oil can result in gear damage and noise.
California Residents: Proposition 65 Warning
Related Categories: Mustang Parts, Mustang Rear Axle, Mustang Differentials, Ford Bronco Parts, Ford F-100 Parts
Installation Difficulty

Intermediate skill is required for this installation.
Installation Instructions
Vehicle Fitment
This product will fit the following Bronco years:
This product will fit the following F-100 years:
- 1948,
- 1949,
- 1950,
- 1951,
- 1952,
- 1953,
- 1954,
- 1955,
- 1956,
- 1957,
- 1958,
- 1959,
- 1960,
- 1961,
- 1962,
- 1963,
- 1964,
- 1965,
- 1966,
- 1967,
- 1968,
- 1969,
- 1970,
- 1971,
- 1972,
- 1973,
- 1974,
- 1975,
- 1976,
- 1977,
- 1978,
- 1979,
This product will fit the following Mustang years: