There have been a jillion different variations of the 9 inch Ford based center section over the years. Different materials, different pinion supports, and different attachment options have been made over the years. And then there are all the different sizes of 9 inch that are available to make them even stronger. With 9.5″, 10″, and more available, there is no lack of strength available in the platform. But what about those folks who are driving their 9″ equipped rides A LOT, and those who are wanting to get the most efficiency out of their 9″ equipped pro touring machines and hot rods?
Detroit Speed’s FN988 is the answer. It’s more efficient than a 9″, quieter, and still maintains the strength that most pro touring folks and hot rodders need.
Detroit Speed FN988 Centersection: Solving the Classic 9-Inch Problem
For decades, hot rodders and performance builders have leaned on the Ford 9-inch rearend for one simple reason: strength. But anyone who has driven one on the highway knows its Achilles’ heel—the infamous gear whine and unnecessary drag that comes with it. Detroit Speed has listened to years of feedback from real-world builders, and with the FN988 center section, delivers a solution that finally bridges the gap: 9-inch strength, without the noise and inefficiency.
What Causes 9-Inch Rearend Whine at Highway Speeds?
The classic 9-inch design is legendary for its durability. Its hypoid gear arrangement provides extra tooth engagement, making it tough enough for serious horsepower. But that same design comes with drawbacks: steep hypoid angles create excessive friction and result in the characteristic “nine-whine” many have simply accepted as part of the package. On long highway drives or spirited cruises, that gear noise can dominate the cabin. And beyond the noise, that friction quietly robs horsepower—a parasitic loss that adds up.
Modern 8.8-inch designs addressed these issues with a shallower hypoid angle, creating a quieter, more efficient differential. But retrofitting an 8.8 into a vehicle originally built for a 9-inch comes with its own headaches: C-clip axles, sealed housings, and far more involved service procedures. Builders have long faced a tradeoff: live with the 9-inch whine, or compromise on strength and serviceability.
How to Get Rid of 9-Inch Gear Whine: The FN988 Centersection
Detroit Speed developed the FN988 to give builders what they’ve been asking for: the best aspects of both designs in one simple, drop-in solution. The FN988 centersection allows an 8.8-inch gearset to operate inside a traditional 9-inch-style removable case. You maintain the familiar 9-inch housing, suspension mounting points, and proven durability—but eliminate the two biggest complaints: noise and drag.
Inside the FN988, you’ll find a premium Ford 8.8 ring and pinion set paired with a 31-spline Eaton Truetrac limited-slip differential. The centersection itself is cast from high-strength nodular iron with forged steel carrier caps, solid pinion spacers, ARP fasteners, and safety wiring—a build spec Detroit Speed customers have come to trust. This isn’t a compromise; it’s an upgrade.
What Are the Benefits of a Ford 8.8 Rearend?
- Quieter Cruising: Thanks to the 8.8’s shallower hypoid angle, the FN988 dramatically reduces gear noise. Long drives are quieter, your stereo no longer competes with drivetrain drone, and cruising comfort improves without sacrificing performance.
- More Efficient Power Delivery: Lower friction means more power reaches the tires. Builders report smoother acceleration and improved responsiveness, with some noting modest gains in fuel economy due to reduced parasitic loss.
- Easy Servicing: The 9-inch-style removable centersection remains, so gear swaps, inspections, and maintenance stay simple. No more C-clips. No need to remove axles or back covers. It’s the serviceability builders know and appreciate.
- Built for Real-World Power: With 31-spline axles and a proven Truetrac differential, the FN988 is designed for serious street/strip builds. Whether you’re pushing a naturally aspirated stroker or a boosted LS, the FN988 holds up under real-world horsepower.
- Direct Fit for Restomods: For builders working on classic Mustangs, F-bodies, trucks, and custom street rods already using a 9-inch housing, the FN988 drops right in. You keep your current suspension and chassis geometry while gaining modern drivability.
What Parts Are Required for Retrofitting?
Retrofitting the FN988 into your existing 9-inch housing is straightforward, but there are a few key parts to account for. The FN988 centersection itself is the core component, housing the 8.8 gearset inside the familiar 9-inch dropout case. Because the differential’s spline location differs from a standard 9-inch, new axle shafts are typically required to ensure proper engagement and fitment. Additionally, the FN988’s pinion sits approximately ¾” further forward compared to a traditional 9-inch, which may require a shortened driveshaft to maintain correct driveline geometry. While these adjustments are minor, addressing them upfront ensures a smooth, hassle-free installation.
The Trusted Solution for Today’s Builder
Detroit Speed designed the FN988 because builders demanded a better answer. Whether you’re cruising to a weekend event, carving corners on the autocross, or just enjoying your restomod on a Sunday drive, the FN988 solves the age-old 9-inch compromises. It delivers the strength you need, the quiet operation you want, and the serviceability you expect—all in a package engineered, tested, and supported by Detroit Speed.
If your project demands modern performance without sacrificing classic durability, the FN988 gives you the confidence to build without compromise. It’s the kind of solution you expect from a company that lives inside the garages of real enthusiasts, solving real-world problems every single day. Shop 9-Inch Rearend Center Section