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Drive shaft safety?


1/2 ton status
Premium Member
Apr 28, 2019
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Long Beach, CA
I've seen both...pole vaulting is usually a product of a soft surface roadway, or a defect in the roadway like a large seam in the concrete. At highway speeds, the shaft will usually fold before the car flips, depending on the suspension and speed. Seeing less and less of these with everything being front wheel drive these day. The ones that don't lodge on something do create quite a bit of damage before breaking free or stopping. Bear in mind, most of the vehicles I've seen did not have the shaft break first, it was secondary damage from some other event. I've only had one break on me, at fairly slow speed, and it just fell on the dirt road and made some horrendous noises that made me see dollar signs. Damage wasn't actually that bad, but driving 35 miles back to the paved road with only the front wheels sucked.

And I stand corrected on the OEMs. I should have said the reason the NHTSA or some other governing body hasn't required them to be installed is because there is a very low instance of injury from the driveshaft breaking at either U-joint and falling to the ground at highway speeds. Lots of damage, though....


The Sticker Guy
GMOTM Winner
Apr 20, 2004
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Northern Colorado
One of my first hard lessons was not using lock washers on the ujoint ubolts in my first K5. The rear driveshaft dropped from the tcase to the pavement. Luckily I was slowing down for a red light so the only damage was a messed up CV.


1 ton status
Premium Member
Jul 31, 2008
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Two stories about this topic:
First, I bought a Honda Passport, awd, new in 2019. Its a front wheel drive car that engages the rear wheels when needed. Very strange system, the rear end is basically a spool. No diff. But both rear axles are driven through electo-hydralic clutches that are computer controlled.
So the power can be directed to which ever wheel needs it, and the wheels can turn at different speeds.
Not long after I got it, I got the chance to put it on a lift. No pictures, did not think of it. But it has a factory stock driveshaft loop just behind the front-rear u-joint.
Not sure what to think about that. Is losing that joint so common on those cars that they would eat the added cost?
Have not needed it yet........

Second story:
In this part of the country, a lot of the back roads use wooden bridges built by the local timber company.
They dig a slot in the road, put wooden bulkheads across each side. If its a wider stream, they drive wooden pilings in the stream, with railroad ties across the top of them.
Then they lay railroad ties across the opening, with the ends resting on the bulkheads and the centers supported by the pilings in the middle.
Usually three ties to the side with the middle open. You do not want to miss the ties, the front of the truck will fall down in the middle opening.
They are called female bridges for obvious reasons.........
Several years ago, two friends of mine were driving out to check on some land. They came up on one of these bridges. It was in good shape, not all that old.
They hit it about 20/30mph.
With no warning whatsoever, the truck suddenly soared into the air, there was a huge jolt, and the next thing they knew, the truck was standing on it's nose, and they were in the floorboards up under the dash.
Both shaken and stirred...
They finally managed to get squared around, and managed to get the doors open. They more or less fell out. One of them was fairly heavy, and when he tried to crawl off the door, the hinges gave way and dumped him on the ground.
Fortunately the front end of the truck sorta flattened out and it was fairly stable and did not fall on either one of them.

What had happened, was the center of the three ties on one side slid off the bulkhead on the far side. As soon as they passed the center support, that end fell down, causing the other end to rise up and catch the underside of the truck. As they continued forward, the tie pole-vaulted them upwards until the end in the ground stopped swinging due to jamming between the bulkhead and the center support. Since the tie had caught the truck behind the center balance point, the front end started tilting down.
At that point, the momentum of the truck was such that it snapped the tie and that caused the truck to drop straight down on its nose.
There was no such thing as cell phones, or digital cameras, so they had to walk, or limp, out about 5 miles to get help. And without pictures, it took the insurance company a long time to believe what happened.
But, word had gotten around before the wrecker got there, so they had lots of witnesses. Quite a crowd gathered to watch the wrecker try to figure out how to get it down without causing more damage.
They finally built a support behind and under the truck, and pushed it back on it. Then jacked and removed the boards until it was on its wheels again.
All for nought though. The frame was so bent, and I think even the motor mounts partially failed and let the fan go through the radiator, the insurance totaled it.
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