If you’ve ever seen photos of an interference engine that has been over-revved, you probably think you know what catastrophic engine damage looks like. This 2021 Jeep Wrangler Rubicon’s engine bay absolutely redefines the concept.
This four-door looks perfectly fine from 10 feet away, as TikTok channel sbcsdime210 demonstrates in its walk-around, but what lurks beneath is an entirely different story. The Drive caught up with the channel’s operator and got the details behind this spectacular failure, and what we’re looking at is the result of user error. This Wrangler was flat-towed behind an RV, which is not at all unheard of. Tragically, in this case, the driver made the critical mistake of leaving the Wrangler in gear. First gear. With the transfer case in 4-low. I can hear some of you groaning in sympathy all the way up here in Michigan.
If you’re not familiar with the mechanical reasons why you absolutely do not want to do this, here’s the short version: The lower the gear in an automobile, the faster your engine spins for a given road speed. Red line in first gear in a typical passenger car is probably no higher than 30 to 35 miles per hour. Doing highway speeds in first gear is simply not possible in most cars, this Jeep included. In fact, vehicles have had rev-limiters in place for decades to prevent drivers from accidentally exceeding an engine’s rated operating range.
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But with a manual transmission, it’s possible to circumvent this protection by shifting into a gear too low for your travel speed, because with the vehicle in gear, there is a mechanical connection forcing the crankshaft to spin far quicker than the rev limiter would otherwise allow. As you creep farther and farther past redline, the likelihood of a failure increases dramatically. In our above example, a car that redlines at, say, 6,600 RPM (like this Jeep) would probably be spinning close to double that at 60 mph in first gear.
That alone would be enough to brick an engine, but what happened here was actually worse than that. This Jeep wasn’t just in first gear; it was in first gear with the transfer case in 4WD Low, which multiples the engine RPM even more for a given travel speed. If you thought 12,000 RPM was bad, well, 50,000 is quite a bit worse. As you can see, the result is something akin to throwing a wet paper bag into a tornado.
In this case, the Wrangler’s engine was ripped to absolute shreds, and it took a good chunk of the transmission housing and several surrounding accessories with it. In the TikTok screenshot we included up top, you’re looking up into two of the Pentastar V6’s cylinders. There should be an oil pan, part of the block, more of the crankshaft and two pistons where we see nothing but a gaping maw instead. We suspect it did a number on some of the driveline components that appear otherwise intact as well, but the engine bay scene is enough to make even a robust savings account head to the locker room early.
The lesson here? When towing, read the manual and check everything twice.
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