What is the diameter of the 8.8 axle?
The diameter most commonly referenced for a Ford 8.8 rear axle is 8.8 inches—the ring gear diameter. The name reflects the size of the internal gear that meshes with the pinion, not the overall outer dimensions of the axle housing, which can vary by model and year.
What the 8.8 designation denotes
The "8.8" in 8.8 axle refers to the diameter of the ring gear inside the differential. This size is the defining feature of the axle family and serves as the key spec when identifying compatible parts or swap options. While the ring gear diameter is fixed at 8.8 inches, other dimensions of the axle assembly are not universal across all 8.8 configurations.
Variations and what to verify
Beyond the ring gear size, axle assemblies can differ in several ways depending on year and model: axle shaft spline count, housing width, and brake or hub configurations. To ensure correct parts for a specific vehicle, verify the exact year, model, and VIN (or consult the official service data) before purchasing bearings, gears, or axles.
Summary
In short, the diameter most people mean by the term "8.8 axle" is 8.8 inches, corresponding to the ring gear. For precise measurements beyond that (such as shaft spline count or housing width), always check the vehicle-specific specifications for your model and year.
