It only takes a flick of a switch to activate the Rubicon air lockers, locking the differential to provide maximum traction. The factory switch only allowed three locker options: off, rear, or both. This served the Jeep well in most situations. Some Jeep owners modify the system to allow independent front and rear operation.
Lockers
The factory air lockers in the Rubicon are not to be confused with ARB Air Lockers. The principle is similar but the construction and reliability are different. In general, an ARB Air Locker is considerably stronger and will stand up to larger tires and extended use.
Along with the lockers, the NV241 transfer case is one of the more important items that separate a Rubicon from other TJ models. The 4:1 low range and no-slip yoke rear output flange makes this transfer case fully trail ready in stock form. In addition to the transfer case, the Rubicon air locker compressors are seen to the left tucked away from harm.
4:1 Transfer Case
The 4:1 low-range ratio in the NV241 Rubicon transfer case is especially useful off-road, especially in a Jeep equipped with a manual transmission. The lower ratio allows more control when navigating difficult trail obstacles. The NP231 transfer case found in all other TJ models runs a 2.72:1 ratio. In chapter 4, these two transfer cases and their options are discussed in more detail.
So Is It Worth It?
In the beginning, buying a Rubicon made sense because the equipment was covered under the factory warranty. The fact that the newest TJ is more than 10 years old means that a warranty is no longer a consideration. Choosing between the two models is never clear. However, purchasing a non-Rubicon model will often save enough money to equip a Jeep similarly with higher-quality components that then results in a better-built Jeep.
For the Jeep owner who only exposes his or her Jeep to mild off-road use and keeps tire sizes within the 33-inch range, a Rubicon will serve the owner well with minimal modifications (such as a lift). Those who are out to modify their Jeeps further and want to push off-road limits will likely benefit from a standard model. In the end, it will come down to the goal of the Jeep and the budget.
This heavily built TJ features many modifications and upgrades while still maintaining its ability to drive on the street. Aftermarket axle upgrades, a lift kit, and larger tires are just some of the items visible on this Jeep.
Pros and Cons to Purchasing a Rubicon
Pros
• The 38-percent difference in transfer case ratio is useful off-road without impacting street performance; this is especially useful in Jeeps equipped with a manual transmission.
• Most TJ Wranglers are factory equipped with a Dana 35 rear axle. This axle has known reliability issues mostly surrounding its C-clip design.
• Factory Rubicon models are just special for their originality.
• The NV241 transfer case doesn’t use a slip-yoke (See chapter 4).
• Factory 4.10 differential ratios are well suited for up to 33-inch tires.
• Factory rear disc brakes.
Cons
• Increased purchase price.
• Off-road abuse by previous owner is more likely.
• Aftermarket selectable lockers are stronger.
• A 4:1 transfer case is less significant with an automatic.
• Regearing for 33-inch or larger tires is often needed.
The Blueprint for Building and Modifying
In this book, I will explore building and modifying a TJ for maximum performance on- and off-road. This dual-purpose need forces us to consider all modifications that may severely impact street driving. Building a Jeep with a purpose will help you stay focused on what’s important for performance and stay within your budget. It’s easy to succumb to parts and size lust; in recent years, Jeep owners have been building their Jeeps larger and larger. In the past, 33-inch tires were considered big; now, with the popularity of the JK and JL, it seems that 37-inch tires are “entry level.”
The Challenge
The reason we take our Jeeps off-road is to put the vehicle and driver in situations that force both to perform at their best to overcome the challenge. This challenge is, in effect, the same regardless of the level of the Jeep’s build. An extensively built Jeep will require increased difficulty to get the same challenge. This cyclical effect is what causes Jeep owners to keep building their Jeeps for the chase of the challenge.
Of course, this cyclical effect causes Jeep owners to spend more money on modifications, which require heavier parts to tolerate the increased loads put on the drivetrain from harder trails. This often results in the increased likelihood of broken parts and damaged body parts. These modifications also result in poor street driving and the need to trailer the Jeep to the trail, adding even more cost.
Of all the modifications possible for a TJ, new tires and wheels seem to stand out more than anything else. Choosing the proper size tire and wheel for your Jeep is an early decision to be made. These BFGoodrich Mud Terrain tires in the 285/75R16 size mounted to 16 × 8 Quadratec Rubicon Extreme wheels are a good fit on a lifted TJ.
Keeping It Real
As stated earlier, the goal is to find maximum off-road and on-road performance. This forces a determination of the reasonable street driving compromise without giving in to the desire for overbuilding. All off-road build components will impact street driving in some way. Much-larger tires cause poor gas mileage unless gears are changed. Larger tires increase stopping distance and are much louder on the street. Many off-road tires handle poorly in rain and snow. Lift kits will alter street ride and handling, in addition to raising the center of gravity.
You shouldn’t necessarily be scared off by high mileage. A well-maintained TJ can exceed expectations of some other vehicles. The 4.0L is known for long life and reliability; the 4.0L in this Jeep with more than 193,000 miles still runs smooth and strong. Higher-mileage Jeeps can save money because their lower purchase cost allows for more to be spent on upgrades.
All these things and more are taken into consideration in the following chapters. At the end of each chapter you will find a “Putting It All Together” seciton, where I lay out the best options for our Jeep.
Unveiling the Project
The star of this book is a 2004 Jeep Wrangler Unlimited that was purchased used in bone stock condition. This white TJ is equipped with a 4.0L I-6, automatic, Dana 44 rear, and disc brakes. At 193,000-plus miles, the Jeep still runs well, likely due to its previous owner’s proper maintenance habits.