Ford Sterling 10.5" Axle Rebuild

1999 Ford F350 Super Duty Custom Differentials

When it comes to axle work, there's no substitute for a good shop staffed by knowledgeable technicians, which is why we chose to have the team at Custom Differentials rebuild our axle.

When it comes to axle work, there's no substitute for a good shop staffed by knowledgeable

There wasn't any particular thump, grind, or clunk that triggered our desire to rebuild the rear 10 1/2-inch axle in our "Workin' Dog" '99 Power Stroke-powered Super Duty. Instead, it was the 210,000 miles on the truck's odometer that made us nervous. The truck is in use almost constantly for business, so if the rear axle failed, the result would be unplanned downtime, which is not a good thing.

We turned to the Naeger brothers at Custom Differentials in Bloomsdale, Missouri. Jeremy, a former Top Truck Challenge champion, and his brother Patrick are axle gurus with 37 years of combined axle experience. They specialize in everything from basic rebuilds to the most extreme custom builds. They can either remove and repair your axle in their fully equipped shop, or you can remove the axle yourself (like we did) and bring it to them for service.

When it came to parts, we contacted the folks at Drivetrain Warehouse. They've been around since 1962 and their product portfolio is incredible. They carry installation kits, gearsets, general replacement parts, limited-slip and locking differentials, hubs, axleshafts, gaskets, and so on, from a number of manufacturers. The beauty of this is that with one call you can get everything needed to rebuild or upgrade an axle.

How did the rebuild go? What did we find in our high-mileage axle? What tricks did we learn from Custom Differentials? Read on.

About The Ford 10 1/2-inch
The 10 1/2-inch (commonly referred to as the "Sterling 10 1/2") is a full-float axle with disc brakes found in 1999-2010 Ford F-250 and F-350 trucks. It weighs in at approximately 333 pounds in single rear-wheel versions. The ring gear diameter and pinion shaft length are both 10 1/2 inches. It has a pinion shaft spline count of 31 and an axleshaft spline count of 35. Compared to its predecessors, the first- and second-generation 10 1/4-inch axles, the 10 1/2-inch axle obviously has a larger ring gear, which improved its overall strength and addressed the premature failure issues of the of the 10 1/4-inch axles when used with 4.10:1 or numerically higher gear ratios. There are a number of limited-slip and locker options available, and there are even aftermarket axleshafts available.

Bottom Line
We now have the peace of mind knowing that unless we do something stupid, our axle will provide years of trouble-free service. Best of all, we chose the downtime for our truck. We hate surprises, and sitting on the side of the road with a blown axle isn't good for the blood pressure or the wallet. Since the rebuild, we've been piling the miles on our truck, and the Traction-Lok has exceeded our expectations. It has provided the added traction our Power Stroke-powered rig dearly needed, and its operation is seamless and chatter-free. We're also digging the beefiness of the Genuine Gear G2 diff cover; it has contributed to cooler diff temperatures.

Custom Diff has the equipment to move heavy axles, so it was easy to get the unit out of the bed of our project Power Wagon and into the work area after the seven-hour trip from the Four Wheeler Midwest Bureau. Once on the stand, the first thing Patrick Naeger did was remove the cover and start disassembling the axle. Once the axle was apart, he steam cleaned the housing.
Custom Diff has the equipment to move heavy axles, so it was easy to get the unit out of t
With the axle apart and on the bench, we could see that our bearings and races didn't have much life left. They were all heavily worn, and massive failure was not far away. When the bearings are worn, typically this means the carrier is loose, which puts a side-load on the axle gear hub. This causes the bore that the axle gear fits into to become loose. Translation: The carrier is shot. This wear is typical for a high-mileage axle.
With the axle apart and on the bench, we could see that our bearings and races didn't have
Here's a photo of one of our heavily pitted bearing races.

Typically, you want to replace everything when doing a rebuild. We used a Genuine Gear bearing kit and an AAM gearset, and we also upgraded to a beefy Genuine Gear G2 aluminum diff cover. The Ford Traction-Lok limited-slip differential was from Custom Differentials.
Typically, you want to replace everything when doing a rebuild. We used a Genuine Gear bea
There's more to the disassembly of an axle than you may think. For instance, the bearing caps must be marked so they can be reinstalled in exactly the same position. In addition, careful attention has to be paid to what thickness shims were used from the factory. Most of the time, using the same thickness of shims will get you in the ballpark for reassembly. Here, the old pinion bearing is removed from the pinion shaft so the shim can be removed and measured.
There's more to the disassembly of an axle than you may think. For instance, the bearing c
Here you can see the old factory differential assembly next to our new Ford Traction-Lok limited-slip. We wanted to improve traction and the Ford unit is an often overlooked option. It does have wear items like the clutch material and a spring washer, but it's a three-spider, heavy-duty unit that has a reputation of being very tough.
Here you can see the old factory differential assembly next to our new Ford Traction-Lok l