At work we had an F450 towed in because the rear wheels locked up. We found the pinion nut backed off and shoved the pinion through the bottom of the case. First time I've ever seen that happen.
I"ve seen the scuff marks on the carrier from the pinion being loose, but never seen one poke out the bottom!
A big truck lost his pinion as I was following on the Interstate years ago. The whole pinion dropped out of the rear! I couldn't avoid it. It hit the transaxle case of my Saab Aero and blew oil all over the turbo and exhaust. The smoke looked like an old Nascar blown engine.
"Yea, she's making a whole lot a noise, but I think we can make it home, lets run her straight down the highway, its a few miles shorter...." A 1/2 mile down the road, a big BOOM, and locked up rear tires. Man what a ride that would have been!
As a lifelong drag racer, I've seen a lot of carnage, even doing a fair bit of my own. I've had the differential spider gears exit clear out of the rear cover, I've sheared the pinion gear head clean off, I've broken the transaxle case clean in two on my VW drag car, spitting the contents out onto the starting line. I've had more axle, and ring & pinion failures than I care to think about. But I don't think I've EVER seen anything like that!
It almost looks like the pinion nut backed off until it ran out of threads, broke off or stripped out the threads holding the nut on. A few of the OEM rear ends under some Dodge pickups had the problem with the pinion nut loosening up. It would start out sounding like a U joint was starting to go bad, but would often just make the noise when you went from forward to reverse (or the other way). On the Dodge truck rear ends, it didn't have to go far enough for the pinion nut to actually come off to cause the problem. Just a couple revolutions of the pinion nut loosening would be enough to allow the pinion to slide back in the case and bind between the ring gear and the case. The operation of the ring and pinion would tend to pull the pinion gear back into the ring gear until the pinion gear would wedge between the case and the ring gear. The binding would cause the rear end to lock up both rear tires. If the truck was rolling at any speed, the case was often the weakest point, not that it mattered much at that point. In the pictures its plain to see the pinion has fallen completely back into the case, to do that, the U joint yoke had to come off the pinion gear as well. This total pinion retaining nut failure event would have also allowed the driveshaft to become free of the rear axle and could have caused additional damage. I can not see if the threads on the pinion broke off, or if the threads holding the nut stripped out, or if the nut simply unscrewed.
In drag racing, most of what I saw was so tore up you weren't sure what happened. I have never seen any gear out the bottom.
I'd consider the engineering and metallurgy of the pinion to be superior! Seeing @squirrel reply to a freed up pinion after his recent escapades is humorous!
[QUOTE="RodStRace, post: Seeing @squirrel reply to a freed up pinion after his recent escapades is humorous![/QUOTE] I didn't think of that. His would not. Ove and mine fell out while driving
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