Worst single part catastrophic failure?

[mpicco]

So, what's the single part which would cause most damage to a car if it fails?

My candidate is the timing belt, specially if it happens at high speed.

 

[gaasc]

An exhaust valve if we're going for damage to the engine. A front rim if we're going for overall damage to the vehicle.

 

[CraigB]

So, what's the single part which would cause most damage to a car if it fails?

My candidate is the timing belt, specially if it happens at high speed.

A timing belt could heavily damage an engine, as long as it's an interference engine. Otherwise, it wouldn't do much.

An exhaust valve if we're going for damage to the engine. A front rim if we're going for overall damage to the vehicle.

A dropped valve is a great way to ruin an engine. I see it from time to time here at the race track.


Speaking of which I have seen all sort of damage here. Snapped suspension components leading to the vehicle going into the wall, exploding transmissions (I'm looking at you Chrysler 727 Torqueflight), but the worst I have ever seen was a SBC that when it went took the transmission with it. When towing the car off the transmission had failed so spectacularly that it had broken the bellhousing and was turning with driveshaft and engine as it was drug along.

 

[GRtak]

A blow out on a front tire at speed can kill the car as a whole if it leads to an accident.

 

[Matt2000]

One failed oil seal on a turbo can cause a spectacular runaway and lunch a whole engine, if you’re really unlucky it could start a fire.

 

[73GMCSprint]

Blower explosions, cranks splitting, throwing a rod all come to mind. Exploding transmissions can be spectacularly terrifying; in a high-HP car they're basically a large grenade which could tear both your car and YOU up.

 

[GRtak]

Add transfer case to the neat explosive ability. It is best when at speed on the expressway and it can lay out a nice line of fluids and parts along the way.

 

[ScarFace88]

A blow out on a front tire at speed can kill the car as a whole if it leads to an accident.

A ball joint failure can do this too.

 

[marcos_eirik]

I nominate camshaft gear failure. That happened to my parent's (P38A) Range Rover 4,6 HSE (Rover V8) a few years back. The gear that drove the camshaft failed, which led to contact between valves and pistons and a catastrophic failure of the engine.

 

[BerserkerCatSplat]

Flywheel failure for sure. At high enough revs, a flywheel that grenades will not only cause massive driveline damage (up to and including lunching the engine as the flywheel remains whips around and bend the crank), but the steel flywheel chunks can enter the passenger cabin with extreme force. People have lost entire limbs due to massive trauma caused by high-RPM flywheel failures.

 

[bone]

my indicator

 

[RdKetchup]

Since the title doesn't specify for cars (I know the first post does), I nominate the "Jesus Nut" on a helicopter:

 

[ScarFace88]

The nut behind the steering wheel.

 

[Spectre]

I'm going to go with (in cars) driveshaft failure at high speed. Catastrophic flywheel failure is done and over so fast it's barely perceptible - there's a boom and in the blink of an eye you are dead or wounded by the extremely high speed shrapnel (or untouched) and it's over - damage is usually constrained to a plane in line exactly perpendicular to the axis of rotation. Meanwhile, if your rear wheel drive car's driveshaft or rear driveshaft on a 4WD driveshaft fails at the transmission end while at speed and disconnects (and you don't have a driveshaft safety hoop or loop,) you now have the flail of God smashing around under the car, through the body of the car, around the passenger compartment interior, often right in line with the front seats, driven by the rear axle spinning down. Cars can actually be torn in half and humans reduced to red jelly by a driveshaft front end failure and the resulting flailing driveshaft.

Second is the front driveshaft failing at the transfer case end on a 4WD vehicle at speed. Here's a video of a mild case of that happening, or rather the damage afterwards.