How does a truck (Dorners) break an axle anyway?

cost cutting.

traditional solid axles have two main bearing options. one is cheap and unreliable. one is much more expensive but pretty much completely reliable. the former has both driving and loading forces born by the same component, with both stresses concentrated at the radius of where the half-shaft gets upset to form the wheel stub. the latter has the load going to the axle tube, and the driving force is transmitted to a driven hub. thus there is only torsion on the half shaft, and only weight load on the axle tube - complete separation of functions, and thus much better fatigue performance.

manufacturers know this of course - cheap axles have been failing at the half-shaft upset point for 100+ years. but they get away with it because the public seem to think it's their fault or they did something wrong or the vehicle was just "old", so they never sue. so what if a few people get killed? settlements cost what? $200k? $300k a pop? but saving $50 an axle spread over millions and millions of axles, hey, that's real bonus/dividend money!

Pretty much every solid-axle truck 3/4 ton or larger uses full floaters and has for decades. The real problem is 1/2 ton or smaller trucks being used like a "real truck" and consequently overloaded. Conventional non-FF hubs are quite durable in a truck that is used within its design parameters, but the truth is that most pickups that are used as trucks are used to carry or pull loads that exceed the design parameters of a 1/2 ton pickup.

nate

Odds are we will never know exactly what broke, if anything. I don't believe either the police or the news media to accurately report anything.

All of the news sites are reporting a broken axle: "Authorities said it appeared that the axle of Dorner's truck broke when he briefly lost control of his Nissan pick-up on the access road, which is intended for use by heavy-duty fire equipment."

I found a link that said was a Titan. Think they only come in half ton. Haven't found anything on whether it was a 2 or 4 wheel drive.

Most of them break out near the hub. (cars included) Most of the time it's from abuse. Tires spinning, then immediately getting traction will snap them. A blow to the side will usually do it also. (ie: sliding side ways/fish tailing and sliding into a curb) If it doesn't break right away, it will usually break later 'cause the blow from the side cracked the axle at the hub.

Yup. Some people don't get the picture of what half a ton is. It's four really big guys or 6 regular guys. With two guys in the cab it means you can only carry the equivalent of 4 guys in the bed.

which is retarded - most ordinary cars can do that. so, as i said before, axles break because they're cheap. that honking great v8 f150 has a cheap axle. you can't exactly fault an owner for being under the impression that it's supposed to be able to handle some work.