TJ Wrangler: ‘Donut Media’ Breaks Down the ‘Peak’ Jeep
TJ era of the Wrangler introduced coil springs, four-link suspension to the off-roader, opening a whole new world to conquer.
Today, the Wrangler scales trails like a mountain goat. Three four-wheel drive systems offer tons of capability, depending on how hard you’re going to go. The Dana axles are solid as the rocks your Jeep’s tires gently caress along the way to the summit. Meanwhile, coil springs and four-link suspension keep you rig together through the toughest terrain. It wasn’t always the case, though. The first years of the Wrangler carried the weight (and old suspension) of the CJ into the rest of the Eighties and early Nineties.
The TJ era would soon change this, though, as Jeremiah Burton of Donut Media goes on to explain.
TJ Wrangler: The Peak of Perfection
“In my opinion, the TJ is peak Wrangler,” said Burton. “It’s the favorite child of the family. It brought back the famous round headlights that were on the CJ. It was the last Wrangler to use AMC parts. And it was the first Jeep to feature the oh-so popular Rubicon package.”
The TJ delivered more than that to the table, though. As Burton says, the engineers wanted this Wrangler to offer more comfort and usability on the paved road, while also beefing up its already established off-road cred.
Spring Into Action
“If you take a gander under the majority of trucks out there on the road, you’ll see that they’re fitted with leaf springs,” said Burton. “Them things have been around since the medieval times, when they were called carriage springs.”
While leaf springs are fine for big payloads, they’re not the best at providing a comfortable ride when not under load. They also aren’t tuneable beyond addition or subtraction of leaves, nor do they provide great flexibility or movement.
Thus, coil springs — in the form of the Quadra-Coil 4-Link System — replaced the leaf springs for the then-new TJ Wrangler. The coils offered everything the engineers wanted: excellent road handling, greater flexibility, and better approach and departure angles. Not to mention the ability to swap coils out for various needs on the trail.
Wrap Your Head, Not Your Axles
“One reason the engineers designed the TJ to use coil springs was that the previous-generation Wrangler had this problem, and it was called axle wrap,” said Burton. “Say you have an engine that’s got a lot of torque. When you go to step on the gas, that torque is transferred from the engine to the drive shaft, to the axles, to the wheels.”
According to Burton, that power causes leaf springs to twist into an S-shape, thus taking away traction. Without a lot of traction, you’re not going to scale rocks very well. You might also end up with broken axles, as axle wrap also changes the pinion angle with leaf springs under acceleration. The new coil springs eliminated axle wrap entirely.
Linking-up the Wrangler
“Not only did the TJ use Quadra-Coil, it used what’s called a four-link setup,” said Burton. “A four-link setup means that your axles are supported by four links: two upper arms connected to the top of the axle, and two lower arms connected to the bottom of the axle, with the other ends of the control arms connected to the frame.”
The result? More stabilization of the front and rear axles when it comes to forward and rearward movement (or, rather, the lack thereof). The links, along with control and Panhard bars, also prevented bump steer, keeping the TJ firmly centered on the chosen path.
TJ: Solid as a Rock
“A part of what makes the Jeep Wrangler so good, from the open trails to the technical rock climbs, are its solid axles,” said Burton. “The Wrangler, to this day, still uses solid axles, no fancy independent suspension.”
The reason? Aside from keeping Wrangler fans happy, the solid axles offer simplicity and strength. Less moving pieces means greater ease of repair, upgrading and swapping. The heavy-duty steel housings offer excellent protection for the gears on the trail, and the axles allow for more torque to reach the dirt.
All in all, the Wrangler’s improved suspension during the TJ era beat a path into the dirt still traveled today.
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