Is it possible to have a Ford 9-inch without an annoying amount of gear whine? Of course, but at what cost? How much time and money are you going to spend chasing down the issue when you can now simply bolt an 8.8-inch center section into your 9-inch housing thanks to the engineers at DSE? Detroit Speed now offers five different gear ratios and a complete assembly that will bolt directly into your 9-inch housing. Complete with forged alloy steel carrier bearing caps, high-strength nodular case, safety wired ARP hardware, 1350 forged steel pinion yoke, and a 31-spline Eaton Truetrac differential, it's built to handle some serious power and deliver it quietly and more efficiently than any 9-inch. *The FN988 Case is compatible with all 8.8-inch gears, differentials, and spools. Alternate options are available. Contact us for custom builds or combinations not listed.
FEATURES
- Patent-pending design utilizes an 8.8 gear set, which is quieter and more efficient than standard 9-inch components
- 31-spline Eaton Truetrac 8.8-inch differential
- Available in the following gear ratios: 3.08, 3.27, 3.55, 3.73, and 4.10
- Continous lubrication of pinion bearings provided by internal oil channels
- High-strength nodular cast iron case
- Premium ring & pinion utilizing ARP ring bolts with safety wire
- Solid Pinion Preload Spacer
- Forged alloy steel carrier bearing caps
- 1350 forged steel pinion yoke with U-bolt kit
- Threaded jack bolt holes in mounting flange ease case removal from axle housing
- Case includes mounting holes for bolt-on accessories
- Designed and engineered at DSE and made in USA
Frequently Asked Questions
The FN988 is a bolt-in centersection that fits a traditional Ford 9-inch housing but uses a quieter, more efficient 8.8-inch gearset. It offers the strength of a 9-inch with the smooth performance of a modern differential.
By using an 8.8-inch ring and pinion with a shallower hypoid angle, the FN988 significantly reduces the friction and gear noise commonly associated with traditional 9-inch differentials—especially at highway speeds.
Yes, the FN988 is designed to fit standard 9-inch housings. However, FN988-specific axles are required and the driveshaft typically needs to be shortened due to a forward pinion location.
The FN988 features a 31-spline Eaton Truetrac limited-slip differential, forged steel carrier caps, and a high-strength nodular iron case—making it ideal for high-horsepower street and strip builds.
Detroit Speed offers the FN988 with 8.8 gearsets in 3.08, 3.27, 3.55, 3.73, and 4.10 ratios. Custom combinations are also available upon request.
FITMENT NOTES
Add REM Isotropic Surface Finishing to increase performance, durability and trouble-free operation.*FN988 specific axles will be necessary and driveshaft will need to be shortened.
Specifications
- Yoke Style1350
- Axle Shaft Spline Quantity31
- ManufacturerDetroit Speed
- Carrier StyleFord 8.8-inch
- Case MaterialNodular Iron
- Case SeriesFN988
- Emission Code4
- Gear Ratio3.08 Ratio
- Product TypeDifferential Assembly
- REM PolishedNo
- Universal 9" Center Section?Yes
- Application Specific?No
