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The Legendary World War II Jeep had Dangerous Engine Flaw

The Legendary World War II Jeep had Dangerous Engine Flaw

Despite one of America’s top generals calling the World War II Jeep ‘America’s greatest contribution to modern warfare’, the little 4×4 wasn’t perfect. In fact, it rolled off the assembly line in 1941 with a terrible design flaw that could have sent soldiers barreling into oncoming traffic.

It is dangerous pull to the left during braking that required some serious counter-steering to avoid veering into the oncoming lane. The steering on a World War II Jeep is dead-simple. The steering shaft—which is connected to the steering wheel—goes into a steering gearbox, which uses a worm gear to change the rotational motion of the steering shaft into a pivoting motion of a pitman arm.

As the end of that pitman arm swings in an arc, it pushes and pulls a drag link (just a long metal rod), which rotates the axle-mounted bellcrank, thus pulling or pushing the tie rods. Those tie rods ultimately rotate the knuckles and the wheels connected to them, allowing the driver to steer.

The problem with this system has to do with a phenomenon called ‘axle wrap’, the tendency of a leaf-sprung axle to twist under braking or acceleration. Since the Willys MB and Ford GPW don’t send a lot of power to the wheels (especially in four-wheel drive), axle wrap under acceleration isn’t really an issue. But under hard braking, it definitely is.

As the driver stabs the brakes, the Jeep’s axle rotates towards the front of the vehicle, and it wants to take the bellcrank along with it. Since the drag link—which connects to the -mounted steering box on one end, and the bellcrank on the other—doesn’t move unless the driver turns the steering wheel, the bellcrank will have a tendency to want to rotate under braking as the axle twists.

This will put the driver’s side tie rod in , and the passenger’s side tie rod in tension, thus turning the Jeep to the driver’s side, potentially into oncoming traffic. As a band-aid, sometime in 1942, Willys Overland and Ford started installing a “Torque Reaction Spring” under the driver’s side front leaf spring pack.

Connected to the leaf spring u-bolts on one end, and the frame on the other, the Torque Reaction Spring was essentially a stiff leaf pack whose job it was mitigate axle wrap under braking, thus preventing that awful pull to the left.

The torque reaction spring helped, but many say it didn’t fix the problem entirely. It really wasn’t until the war ended and Willys Overland launched its civilian model Jeep—the CJ-2A—that fixed the problem by taking the bellcrank off the axle and bolting it to the front crossmember. Willys Overland fixed the design flaw by mounting the bellcrank to the tubular crossmember on the Civilian model CJ-2As.

While this setup wouldn’t seem to be as sensitive to axle wrap as the World War II Jeep’s design, it also leaves quite a lot of steering components hanging low to the ground. Presumably, the change to an axle-mounted bellcrank was seen as a benefit from an off-road durability perspective. Unfortunately, that move ended up being arguably the Willys MB’s and Ford GPW’s biggest design flaw. And even today, when collectors smash the brakes on their classic World War II Jeeps, they keep their hands ready to crank that spindly little steering wheel to the right. Because the last thing you want to do is wreck a vehicle as glorious as a World War II Jeep.

Source: https://jalopnik.com/the-legendary-world-war-ii-jeep-had-a-dangerous-enginee-1797186236

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The Legendary World War II Jeep had Dangerous Engine Flaw
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The Legendary World War II Jeep had Dangerous Engine Flaw
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Despite one of America’s top generals calling the World War II Jeep 'America’s greatest contribution to modern warfare', the little 4x4 wasn’t perfect. In fact, it rolled off the assembly line in 1941 with a terrible design flaw that could have sent soldiers barreling into oncoming traffic.
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