Major body rust is not common except with the most neglected and weathered Jeeps. If you find a Jeep with major body rust, it will likely also have major frame rust. Staying clear of these Jeeps might be the best advice unless the price is right and your restoration skills are up for the challenge.
Engine
It’s likely that a TJ will have a 4.0L I-6; it is a more desirable engine compared to the standard 4-cylinder engines found in some X and SE models. The 4.0L engine is extremely reliable and will live a long life when maintained properly. Even in stock form the engine is very capable and power output is well balanced for even hard off-road use. For those looking to do an engine swap, finding a TJ equipped with a 4-cylinder will save extra money.
A rusted-through frame on a Jeep can be big trouble, while normal surface rust is relatively harmless. Many TJ frames rust from the inside out and it’s often too late by the time you see it. Notable rust areas are the rear section of the frame and at the frame mount of the rear control arms. Keeping the frame clean, both inside and out, will help with preservation.
When looking at a used Jeep, look for leaks on or under the engine. Minor leaks are normal due to age and can often be easily remedied. Easy starting and smooth, quiet running are typical signs of a well-maintained engine.
With the Jeep running, check the dash for proper temperature, oil pressure, and charging readings. In addition, a check engine light that is on can indicate trouble. The computerized engine of modern vehicles is a double edge sword. These engines are equipped with many sensors that can malfunction with age, which then results in expensive diagnostics and repair. Reading the code with a code reader or through the speedometer using a particular key combination often results in a vague answer raising more questions.
The illuminated check engine light isn’t something to be ignored. Auto parts resellers can often determine the problem for free using the OBD port and a code scanner. Sometimes the problem can be as simple as a loose gas cap or bad sensor.
Transmission
Choosing a manual or automatic will be a matter of preference. The TJ series used eight different transmissions through the years with the best coming in the last few years with the NV3550 manual, NSG370 manual, and 42RLE automatic. In general, all of the TJ transmissions were reliable and capable, and none should be particularly avoided. The later models are labeled “best” because of their increased heavy-duty capabilities.
A drive test is the best way to determine the shape of a transmission. If it operates smoothly through all gears and shows no signs of leaks below, it may be in good shape. On automatic-equipped Jeeps, smelling the transmission dipstick can indicate condition. The presence of a burned smell and fluid that is dark brown/black can indicate the transmission was overheated, potentially leading to an expensive repair.
Pulling the dipstick and examining the color and smell of the fluid can indicate the condition of the automatic transmission. Deep brown or black fluid with a burned smell can indicate that the transmission hasn’t been serviced for some time or has been overheated.
The Dana 44 was available as standard equipment in a few models of the TJ, most commonly seen in the Rubicon and Unlimited. The Dana 44 is easily identifiable by its egg-shaped cover, compared to the oval shape of the Dana 35 and the rounded shape of the Dana 30. This differential uses the semi-floating style of axle shafts and an 8.5-inch ring gear.
Rear Differential
The Dana 44 with disc brakes was an option on most trim levels through the entire run of the TJ. When looking at buying a TJ, being able to spot a Dana 44 rear is helpful and will add to the value. The Dana 44 is much stronger than the Dana 35. Moreover, the design difference doesn’t use the C-clip axle retention as found in the Dana 35; that’s a definite advantage.
Previous Modifications
Purchasing a Jeep that has been already modified can save money, especially if the modifications were done properly. A downside to existing modifications is that the Jeep may have been used hard off-road, something easily spotted by examining the condition of the skid plates. Deep scrapes underneath usually indicate rock crawling, which may not be a problem, but it is a good indicator of previous use.
Extensive suspension modifications such as long-arm kits by a previous owner can be a cause for concern. Even when installed properly, these can dramatically impact street driving. Often, long-arm systems relocate the control arms that are sometimes bolt on or weld on. Weld quality with suspension systems is extremely important from both a performance and safety perspective. A test drive through varying road conditions will indicate the stability and performance of the system.
Wiring hack jobs can be a nightmare to diagnose and can present a fire hazard when not installed correctly. Look for random wiring under the hood and under the dash. If possible, determine the purpose of the wiring from the previous owner.
This Wrangler TJ Rubicon has a good balance of on- and off-road capability. The factory Rubicon Dana 44 rears are equipped with factory lockers and 4.56 gears. Combine these with a 3-inch lift and 33-inch tires and you will maximize off-road capability while keeping streetability.
Take a Friend
When setting out to look for a Jeep, take a Jeep friend along to serve as a voice of reason and a second set of eyes. Discuss what each will look for before arriving at the potential new purchase. Make the friend promise to not let you purchase the Jeep if too many red flags come up. The team approach to a purchase (or not) will typically result in the best decisions.
Rubicon Versus Non-Rubicon
A common question is “Should I buy a Rubicon?” The answer is not always clear, but usually it involves two things: How much will you spend on the initial purchase? How will you use the Jeep? A Rubicon will fetch a much higher price than a standard model. The most important things that set the two models apart are:
• Air locker–equipped front and rear Dana 44 axles.
• 4:1 NV241 Transfer Case
• Rear disc brakes
• Authentic Rubicon Hood Decal
• Special Moab wheels with larger tires
All other Rubicon features are less important, such as the marginal factory body protection, extra skid plates, and 1-inch-wider flares. The 16-inch Moab wheels and factory rear disc brakes are a nice feature. The factory rocker guards are relatively light-gauge steel to keep weight down, but they offer minimal improvement to side protection. Many Rubicon owners replace them with aftermarket heavier rocker guards.
Dana 44 Axles
The Dana 44 front in a Rubicon is more a Dana 30 with a Dana 44 center section. The axle shares outer components with the Dana 30, including axle shafts and knuckles. Axle tubes in a Rubicon Dana 44 are considerably smaller in thickness and diameter than a true Dana 44 front. In reality, a Dana 30 will withstand a considerable amount of trail abuse with 35-inch tires or smaller. Aftermarket axle shafts and trusses can significantly upgrade both the Dana 44 and 30.