Most drivers expect serious engine trouble to come with obvious warning signs, such as loud knocking, smoke, dashboard lights, or a breakdown that happens all at once. But according to one mechanic on TikTok, some of the worst damage can build quietly over time, all because of a problem most people would never think to look for.
A viral video shared by TikTok creator @davesautocenter breaks down a failed LML Duramax engine and shows just how destructive one crankshaft-related issue can become. During teardown, the mechanic reveals that the crankshaft had snapped completely in half, a catastrophic failure that points to a deeper balancing problem inside the engine.
A Tiny Weight Difference With Huge Consequences
In the clip, the mechanic explains that the pistons in the engine had a ten-gram weight difference between them. On paper, that may not sound like much. But once an engine is spinning at high RPMs, even a small imbalance can create massive force.
He says that at around 3,500 to 4,000 RPM, that difference can effectively translate into around twenty pounds of force, repeatedly stressing the crankshaft. That means what looks like a minor mismatch during assembly can turn into relentless punishment once the engine is actually running.
It’s the kind of detail most drivers would never notice, but inside the engine, those forces add up fast. And when parts are not properly balanced, the crankshaft ends up absorbing more stress than it was ever meant to handle.
Why the Crankshaft Eventually Failed
What makes the explanation so striking is how often that force is applied. According to the mechanic, at 4,000 RPM, those pulsing loads can hit the crankshaft journals roughly sixty-six times per second.
That repeated impact can wear down components quickly, especially in an engine that already has balancing issues. Over time, the stress becomes too much, and the result can be catastrophic. In this teardown, that’s exactly what happened: the crankshaft broke in half.
The mechanic also suggests that the crankshaft design itself can already be vulnerable in this type of setup, making proper balancing even more important. When the engine’s internal parts are not matched closely enough, the risk of failure goes way up.
Watch the Mechanic Break It Down
@davesautocenter Crankshaft Dynamics, Engine Killer #autoshop #autorepair #enginebuild #carrepair
Why This Video Is Getting So Much Attention
What makes this mechanic’s explanation hit so hard is how it turns a highly technical issue into something people can actually understand. A ten-gram difference sounds small until you hear it described as repeated hammer-like force hitting the crankshaft dozens of times every second.
That’s also why so many people are drawn to teardown videos like this. They reveal the hidden side of engine failures, the kind of damage that doesn’t always come from one dramatic moment, but from a buildup of stress that keeps getting worse until something finally gives.
For truck owners, diesel fans, and anyone interested in how engines actually work, it’s a pretty eye-opening reminder that precision matters more than most people realize.
Why Drivers and Builders Should Pay Attention
The bigger takeaway here is that engine reliability depends heavily on balance and precision. Small differences in internal components may seem minor at first, but under real operating conditions, they can create serious long-term damage.
That’s especially true in engines that see higher RPMs or heavy use, where even slight imbalances can put enormous strain on rotating parts. And while the average driver may never tear down an engine themselves, videos like this make one thing very clear: sometimes the most destructive problems start with details that seem far too small to matter until they matter a lot.
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