OS Giken FD881-HA Super Lock LSD for Ford 8.8in IRS 31 Spline Mustang Cobra

Vehicle Fitment

• Compatible with all Ford 8.8" IRS (Independent Rear Suspension) differentials - 31 Spline axle configuration
• 2001-2004 Ford Mustang SVT Cobra - 4.6L V8 Supercharged, IRS, 31 Spline
• 2003-2014 Ford Mustang GT / V8 - 4.6L / 5.0L V8, Solid Axle, 31 Spline
• 2011-2014 Ford Mustang V6 - 3.7L V6, Solid Axle, 31 Spline
• 1989-1997 Ford Thunderbird Super Coupe - 3.8L V6 Supercharged, IRS (28-spline stock carrier; 31-spline requires carrier swap)
• 1993-1998 Lincoln Mark VIII - 4.6L V8, IRS (28-spline stock carrier; 31-spline requires carrier swap)
• 2000-2006 Lincoln LS - 3.9L V8, IRS, 31 Spline
• 1998-2002 Ford Explorer / Mercury Mountaineer - 5.0L V8, IRS variants, 31 Spline

Fitment Notes

• Designed specifically for the Ford 8.8" differential housing with 31-spline axle shafts - does NOT fit 28-spline configurations
• Compatible with both IRS (Independent Rear Suspension) and solid axle 8.8" housings equipped with 31-spline carriers
• 1989-1997 Thunderbird and 1993-1998 Lincoln Mark VIII came from factory with 28-spline carriers; a 31-spline carrier swap is required for fitment
• 1999 Mustang SVT Cobra used a 28-spline carrier and is NOT compatible without a carrier swap; 2001-2004 Cobras used 31-spline and are directly compatible
• Does not fit the 2015+ Ford Mustang Super 8.8" differential (34-spline)
• SPEC-S (standard) configuration as listed; SPEC-X (track-only custom tune) and TCD (enhanced oil-cooled disks) available as separate order options
• Refer to OEM service manual for installation; no break-in period required

Features

• Patented pressure ring design delivers smooth, progressive 100% locking capability with low preload - open-diff feel at street speeds, full lock under load
• Spline-through-side-gear construction accommodates up to 2x more friction plates than competing designs - up to 28 total plates for superior locking force and reduced heat
• All components chemically heat treated and constructed from high-grade steel alloy for maximum durability under sustained street and track use
• Gears are raw-forged for maximum strength; clutch disks are precision-machined on both sides simultaneously to extremely tight tolerances for minimal warpage
• LSD case machined from a single billet piece for uniformity and rigidity; cone spring relief cut-out minimizes cone spring degradation
• Fully tunable: initial torque, lock timing, ramp angles, and disk spec all adjustable in-house by OS Giken

Specifications

• Part Number: FD881-HA
• Configuration: SPEC-S (Standard - street and track use)
• LSD Type: Clutch-Type Limited Slip Differential (1.5-Way)
• Differential Housing: Ford 8.8" IRS / Solid Axle
• Axle Spline Count: 31 Spline
• Ramp Angles: 25° / 35°
• Lock Timing: 336
• Total Friction Plates: 20
• Preload: 10S
• Position: Rear Differential
• Package Weight: approx. 28 lbs
• Manufactured: 100% in Japan by OS Giken

Included Components

• 1x OS Giken FD881-HA Super Lock LSD Unit (SPEC-S)

Product Description

The OS Giken FD881-HA Super Lock LSD is a purpose-built limited slip differential engineered for the Ford 8.8" rear axle platform with 31-spline axle shafts. Compatible with both IRS and solid axle 8.8" housings, it covers a wide range of high-performance Ford applications including the SVT Cobra, Mustang GT, and Lincoln LS. OS Giken's patented pressure ring and spline-through-side-gear design accommodates up to 28 friction plates - far exceeding competing clutch-type LSDs - delivering dramatically improved locking force, smoother engagement, and significantly less heat buildup. At street speeds the unit behaves like an open differential; under load it locks progressively and fully, directing power to both rear wheels for improved launch traction, corner exit stability, and consistent drift or track behavior.

Built entirely in Japan from chemically heat-treated, high-grade steel alloy with raw-forged gears and a single-billet LSD case, the FD881-HA requires no break-in period and no scheduled rebuild. Tuning options including cone spring preload, pressure ring spring stiffness, and ramp angle swaps are all available directly through OS Giken USA. Confirm axle spline count before ordering - this unit is for 31-spline applications only.