Detroit Speed Assembled Center Section FN988 Torque Arm 31 Spline 070881-308DS

The Detroit Speed FN988 Torque Arm Differential delivers exceptional performance for 3rd and 4th Gen Camaro and Firebird applications, combining the quiet efficiency of the Ford 8.8 gear set with a dropout center section and integral torque arm mount. While the Ford 9” is known for strength and reliability, its pinion design sacrifices smoothness and efficiency - issues the 8.8” addressed over 40 years ago. The FN988 merges the best traits of both, offering a refined, high-strength differential solution with a 31-spline Truetrac, 1350-series yoke, and five gear ratio options. Engineered, tested, and proven by Detroit Speed, it delivers modern driveline control, durability, and performance for Pro Touring and high-output street builds.

ENGINEERED FOR STRENGTH

Detroit Speed’s FN988 Torque Arm assembly sets the standard for precision and performance in differential design. The integrated torque arm mount eliminates the need for additional brackets common in 9” axle housing swaps, improving the tight packaging constraints in 3^rd/4^th gen F-Bodies. Each case is cast from high strength nodular iron and machined to exacting tolerances. Forged steel bearing caps further increase strength in high horsepower application. Assembled with a 31 spline True-Trac Differential, Ford Racing gear sets, high quality bearings and heavy-duty 1350 yoke ensures durability under modern power levels, making it ideal for high-horsepower LS and LT builds

TRUSTED BY TOP INDUSTRY PROFESSIONALS

Designed with professional builders and advanced enthusiasts in mind, the FN988 is trusted and used by many of the highest quality build shops in the country. The quiet, efficient operation offers a level of refinement consistent with the high quality builds across the country
Its precise geometry, housing alignment, and superior materials make it the perfect foundation for Pro Touring and performance builds requiring exact tolerances and modern driveline control.

OPTIONAL REM POLISHED GEARS

Detroit Speed offers REM polished gear sets to further improve the operation of the rear differential assembly. Look for “-R” on the part number for optional REM treatment. 

What is REM treatment? This polishing process creates a smooth micro-textured surface on the gearset for enhance oil retention properties. Commonly used by racing professionals looking for every advantage, the result of REM treatment is reduced heat and friction, increased component life, and quiet, efficient operation.

FEATURES & BENEFITS

• Engineered for Strength – Nodular Iron and Forged Steel bearing caps for high horsepower reliability.
• Quiet, Efficient Operation – transmit more power to the tires while eliminating gear whine.
• Ease of Installation – Dropout center installs into 9” housings and eliminates C-Clip axles
• Integral Torque Arm Mounting – Refines the packaging and installation of a 9” housing in 3^rd/4^th gen camaro applications.
• 31-Spline Truetrac Differential – Delivers smooth, predictable power distribution and superior traction.
• 1350-Series Yoke – Heavy-duty construction for high-torque durability.
• Built to Detroit Speed Standards – Precision-assembled for performance, reliability, and perfect fit.
• Multiple Gear Ratio Options – 3.08, 3.31, 3.55, 3.73, and 4.10 gear ratios available, refer to part number for specific ratio.

FITMENT NOTES

• Fits: 1982–2002 Chevrolet Camaro & Pontiac Firebird (3rd & 4th Gen F-Body) with 9” axle housings
• Compatibility: Detroit Speed torque arm rear axle housing
• Differential: 31-spline Truetrac
• Gear Ratio: 3.08
• Yoke: 1350-Series
• Ideal For: Pro Touring, high-performance street, and competition builds