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Nuts & Bolts: I Keep Breaking the Locking Hub Studs

Posted in How To: Tech Qa on March 15, 2016
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Photographers: 4-Wheel & Off-Road archives

Breaking Toyota
I have a Toyota pickup that regularly breaks locking hub studs. All six go at the same time, including the dowel pins. I have ARP super metal studs in there now, and I have broken them three times. Prior to this I had broken stock ones twice, and I have literally blown a hub off the truck. The truck has 35-inch tires (that actually measure out to 33s), 22RE, 4.7-geared t-case, 5.29s, high-pinion and a Grizzly locker in front, a Detroit Locker in the rear, Bobby Longs, and hi-steer, just to paint the picture. We wheel hard, but my buddies have never broken these the way I have. I have a ladder-traction bar on the rear axle to prevent axlewrap. It works great. Could it be stressing the front end somehow? All our brains together and this is all we can come up with.
Andrew F.

You didn’t mention if it’s the same side that’s always breaking, but even if it’s not, that’s a lot of broken hub studs! Assuming that you’ve been installing everything properly (cone washers on all the studs, new dowel pins, and so on), we suspect you have something else going on. We posed your question to a couple of Toyota axle experts to see what they had to say.

A technician at All Pro Off-Road ( suggested inspecting the hub stud holes in the wheel hub, especially if it’s the same side that keeps shearing the studs. If the hub was run loose at one time, those holes could be wallowed out and causing the studs to work themselves loose. He also recommended closely inspecting the holes in the hub body where the cone washers install. Again, if the hub was run loose at one point or the hub was repeatedly removed improperly, those holes could become egg-shaped and prevent the hub assembly from maintaining a consistent torque.

The guys over at Marlin Crawler ( said that because you’ve broken so many stud sets (including multiple ARP sets), they would be willing to bet money the dowel pin holes in the body of the locking hub or the wheel hub have gotten wallowed out. When this happens, the dowels can’t do their job and all of the torque load transfers to the studs. This is especially true when all six studs and the dowels fail at once. They suggested that new locking hub bodies and fresh hardware (including dowel pins) should solve the problem. Although it’s not on the company’s website, Marlin Crawler does offer a six-pin hub conversion, which adds four dowel pins per hub assembly and makes the assembly virtually bulletproof. The conversion would require you to send in your wheel hubs and locking hubs to be drilled to accept the additional dowels. Although this conversion is only needed for really extreme use, it is another potential solution. Good luck, and let us know what you find.

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