We have written so much about the current Wrangler, we wouldn’t be surprised if we babble “JK” in our sleep. This isn’t the first article you’ve read on the Jeep JK. However, our obsession is not without good reason. The Jeep JK is America’s favorite 4×4. Even with the new JL now on the scene, used sales of the JK show no sign of slowing down.
Admittedly, many JKs never hit the dirt. But make no mistake, they’re an excellent choice for the trail. In four-door form they’re big enough to comfortably haul friends and gear without feeling cramped. They boast just right the dimensions to slip through most obstacles on the trail without metal getting mashed. As a huge bonus, the Jeep JK has the most aftermarket support of perhaps any vehicle on Earth. The world is your oyster when it comes to bumpers, armor, suspension, and anything else you can think of.
While the JK wins popularity contests by a big margin, it’s not completely bulletproof. Like any vehicle that gets used in the dirt, it does have some weak points. The harder a JK is used, the more chance these weaknesses will become exposed. Some are worse than others, and can leave you in a lurch if not addressed. Others are simply annoying, but still worth a fix.
The good news is the JK has been around long enough that these weak points aren’t exactly a mystery anymore. Even better, the aftermarket has responded in kind to eliminate them. A whole host of parts are available to strengthen your JK and resolve any of its shortcomings. With the right parts, you can wheel without worry. Let’s take a look at some of the weaknesses of the JK and how to eliminate them.
The biggest sore point on the Jeep JK is its front Dana 30 axle. For tooling around dirt roads and mild trail work it is fine. But start using it harder and running bigger tires, and it will definitely become a fail point. One of the first steps to strengthening the Dana 30 is replacing the factory shafts with stronger chromoly units. These G2 Placer Series Jeep JK shafts are built out of better heat-treated 4340 chromoly, and they accept the beefier 1350-style u-joint found in Rubicon models. They come fully assembled for easy replacement with Dana Spicer u-joints and full circle clips.
The factory ball joints on the Dana 30 are also a known weak point. They use plastic liners that disintegrate during harder use. The result can be death wobble and sloppy handling. Upgraded joints, like those from Synergy Manufacturing, G2, or Dynatrac, are much stronger and do away with the plastic liners.
Besides having weak internals, the Dana 30 axle housing is prone to bending. Bigger tires mixed with tougher terrain compounds the problem. To keep the housing straight, a truss is needed. Make sure that whatever truss you use also reinforces the Cs of the axle, as this G2 truss system does, as they are weak too.
By now you might be wondering, why even bothering throwing money at a Dana 30? If you’re going to be running larger than 35-inch tires we would say don’t bother. There is only so much strength you can add to it. A better solution is to replace the front Dana 30 entirely with a CORE 44 from G2 Axle & Gear. It eliminates the fail points of the Dana 30 with a much stronger housing made from 3-inch diameter, 5/16-thick DOM tubing. A larger new-generation Rubicon Dana 44 ring and pinion is also used. All the brackets are thicker and it includes heavy-duty ball joints.
The brackets on the Dana 30 front and Dana 44 axles are made of fairly thin, stamped pieces. Start running a JK harder off-road with larger tires and they can crack or deform. The front track bar brackets usually see the most abuse, so we would recommend replacing them with upgraded mounts like these from Rubicon Express. They feature thicker ¼-inch and 3/16-inch steel.
For those planning to abuse their JK and run big 40-inch tires, the Ultimate Dana 60 is a seriously stout solution. It uses 35-spline 4340 chromoly shafts with stout SPL-70 u-joints along with a 10-inch ring gear. All of the brackets are upgraded along with 3.5-inch diameter, .370-inch thick axle tubing. It comes with big brakes and is available with an Eaton ELocker, or an ARB Air Locker.
An item in a fairly exposed location at the back of the JK is the factory muffler. Wheel enough and eventually it will get bashed. Again, it probably won’t end your day, but can cause drivability issues if it’s smashed enough. Look for an aftermarket exhaust that uses a smaller muffler and tucks it up higher in the factory location or relocates it completely like this AFE exhaust system does.
The underside of many modern vehicles leave a lot to be desired in terms of protection and the JK is no exception. Sitting rather exposed and just waiting to be taken out by a rock is the evaporative canister. While it’s not something that will end your day of wheeling, it is a pain and replacing it constantly can add up. You can either guard it with a skid plate or relocate it to a better location. We recommend adding a skid plate for the gas tank as well. A wide array of skid plates are available to protect any squishy parts under your JK.
Start running big and heavy tires on a JK and your steering has a hard time handling the extra weight. Not only does this lead to a hard time steering on the trail, it puts a lot of extra stress on your steering box. While you might get away with 37s, if you are running 40s a ram assist steering setup should be considered mandatory. This one from PSC includes a better pump, a better steering box and a ram that will make steering your big-tire JK easy.
Earlier Jeep JKs were known for overheating issues with the transmission. The main cause is because the transmission cooler is integrated into the radiator. As engine temperature came up, so did the transmission temperature or vice versa. And since the integrated cooler is fairly small, it can’t handle the heat leading to fluid temperatures that are way too high. The only way around this is to run a larger cooler like this Mishimoto unit that is separate from the radiator.
The factory headlights on the Jeep JK are worthless. We have driven cars from the 1970s with better headlights. Okay, this one isn’t a weakness, but more of an annoyance. In a city or well-light suburbia the JK’s headlights might be fine, but once out in the sticks or on a trail they are woefully inadequate. While many go straight for a light bar, we like to upgrade to LED headlights first, like these awesome KC Gravity Pros. That way we can enjoy better light all the time, legally. If you need more light, you can always add a light bar.
The factory tie rods and track bars really aren’t up to hard use. These aren’t items you want to break or bend on the trail, either. It can lead to a very long trail fix, or much worse, a crash resulting from zero steering control. Even if you aren’t running that large a tire, we still recommend upgrading the track bar, tie rod, and drag link to much heavier-duty versions like these from Rubicon Express.
The extra set of doors on the Jeep JK Unlimited have really transformed the Wrangler from a trail toy to a useful daily driver. However, all that extra wheelbase leaves lots of exposed rockers that can be easy to mangle on the trail. One of the first mods should be a nice set of quality rocker protectors to protect the vulnerable area.
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