Rear axles are something we don’t think about often. In fact, rearends are likely the most uninteresting part of a classic Mustang until they fail, or until a sparky upstart blows your doors off at the traffic light, and then you’re wishing you had a set of 3.91 gears. When rearends fail, they leave us stranded, or they follow us home in noisy protest.
Ford removable carrier differentials perform reliably for thousands of miles with minimal maintenance. Keep the differential serviced with proper lubrication, and you can expect more than a quarter of a million miles without a complaint.
We’re going to focus on the Mustang’s basic V-8 and large six differential—the 8-inch removable carrier unit. The 8-inch differential sports an 8-inch ring gear (hence the name) in a wide variety of ratios ranging from 2.50:1 to 4.11:1. Most common are 2.80:1 and 3.00:1 for small-block Mustangs. We’re going to show you how to rebuild an 8-inch removable carrier differential by covering the basics of how to do this in your home garage.
At first glance, a differential can be an intimidating sight. It’s just downright overwhelming if you’ve never tried it before. We looked to Mitch Jackson of A&M Gear Service in Southern California for guidance on our 8-inch chunk from a ’67 Mustang. Jackson told Mustang Monthly that most differentials wear out due to neglect. He added that the most common wear item is the pinion pilot bearing, which generates the most noise when it fails. If the ring-and-pinion gears are initially properly lapped, they can live a long time, he tells us.