How To Build Ford's 9.75 Axle
The 9.75 is a new kid on the Ford axle block. It debuted in 1997 and found a place in Ford's uprated-capacity 1/2-tons. Its primary home is in the new-generation F-150s with the higher GVW package or 5.4L V-8, but it can also be found under the '98-'02 Ford Expeditions and Lincoln Navigators. It's also been used in the limited-production 4x2 Ford SVT Lightning hot-rod pickups. There is an IRS version that replaced the beam axles in the '03-and-up SUVs.
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You can see the detailed axle specs in the nearby sidebar. It's a pretty beefy axle for a 1/2-ton. Big ring gear. Big axleshafts. Stout housing. In torque capacity, it's ahead of the legendary Dana 60, though it's a bit shy of the average semi-floating D60 in load-carrying ability. When you see it, you'll say, "Ah, a downsized Sterling 10.50!" and you'd be pretty close to grasping the concept. Other notable comparisons to the Dana 60 are that the 9.75 has about the same-size carrier bearings and larger pinion bearings.
The 9.75 has had a few changes in its relatively short life, including larger axle bearings and shafts in '99 (from a 1.620-inch inner diameter to 1.705 inches), a larger outer pinion bearing (increased from 1.31 x 2.68 inches to 1.31 x 3.00 inches), and the pinion was altered for a longer crush sleeve.
With the new-generation F-150s outnumbering everything but corner convenience stores, we thought it useful to look at this axle from a builder's/swapper's perspective and see what can be done to make it better. To that end, we enlisted the aid of the University of Northwestern Ohio's High Performance Drivetrains class to install just about every goodie currently available for the 9.75. This school is located in Lima, Ohio, and has a high-performance motorsports program beyond compare.