Jeep Wrangler Rubicon 392 Essentials
The launch of the Jeep Wrangler Rubicon 392 was momentous in many ways. Most importantly, it marked the first time in the Wrangler’s history that it would come from the factory with a V8. Originally unveiled as a 2021 model year, it was suspected that the 392 would be short lived. However, with the 2024 order banks now open, we are happy to report that, as of now, the 6.4L Hemi option is still available. While this Jeep is by far the most powerful and capable Wrangler ever produced, it’s not without shortcomings.
As the most expensive Wrangler ever offered, it may be hard to imagine why you would need to invest even more in the 392 platform. Though we feel Jeep got the majority of the details close to perfect, our real-world experience has taught us that there are a few key areas worth upgrading. In this article, we’ll go over some of the flaws on the flagship Jeep and what we did to address them.
37-inch Tires
Jeep not equipping the Rubicon 392 with a 37-inch-tall tire is a major missed opportunity. With a two-inch factory lift and highline flares standard, the aesthetics (along with off-road performance benefits) of a 37-inch-tall tire just makes sense. We’ve found you can run a true-to-size 37x12.50R17, such as the Nitto Recon Grappler A/T shown, by simply installing two-inch bumpstop landing pads on the rear axle.
Gear Bump
While 35’s and 4.56 gears are now standard on the 392, the first run of the Hemi-powered JL just came with 33-inch-tall tires and 3.73 differential gears. A 37-inch-tall tire matches well with the factory 4.56 gears, but you’ll notice more of a performance loss with 3.73 and taller rubber. As we mentioned, if you want to run a 37-inch-tall tire, you’ll need a 2-inch bumpstop landing pad, such as the one from JKS Manufacturing shown on the left. If you are just looking to run a 35 (which is better suited with the 3.73 ratio), you just need a 1-inch bumpstop pad, such as the one from the Xtreme Recon package shown on the right.
Tazer Time
If you make any adjustments to the gearing or tire size, you will need a module to update these changes into the computer. The best device we’ve found for doing this is the Tazer JL Mini from ZAutomotive. This device allows you to modify and unlock a tremendous number of features on the Wrangler platform in general. Two of the most important for the 392 is having the ability to place the transfer case into two-wheel-drive and completely shutting off all of the traction control nannies.
2WD Option
From the factory, the 392’s MP3022 transfer case does not give you the option to have 2WD, despite that setting being available with this T-case in other Wrangler models. With the Tazer installed, you can access the 2WD feature by engaging an option that reads FORCE RWD. Putting the 392 in 2WD makes for a better driving experience overall as it lights up the steering feel and preserves the life of the clutch inside of the transfer case (more on that next).
Transfer Case
One of the biggest issues we’ve seen with the 392 has to do with the aforementioned MP3022 transfer case. Specifically, the clutch that’s used to send power to the front driveline. In the 392, the 4AUTO default setting uses throttle input and wheel speed to adjust the percentage that the clutch engages. In 4HI and 4Lo, the clutch pack “locks” together to send consistent power to the front end. Clutch packs are a wear item and we’ve seen numerous cases where the packs are failing with fairly low miles on the platform. While the aftermarket is working on a few solutions for this issue, a good way to prolong the life of the clutch is to avoid using 4AUTO and primarily drive the Jeep in 2WD using the Tazer.
Suspension Lift
If you want to increase the trail performance and ride quality of your 392 an aftermarket suspension is worth investing in. The factory suspension is poorly equipped to handle the weight of the V8 engine off-road and leaves a lot to be desired when it comes to suspension travel overall. We’re running a 2.5-inch lift from JKS Manufacturing, which gave us an additional 1¾ inch lift over the stock suspension. This resulted in more ground clearance, a level stance, and increased suspension travel.
Shocks
While moving away from the factory suspension is a step in the right direction, to get the most out of your upgrade, you’ll want to invest in a quality set of shocks. We prefer Fox 2.5 Performance Elite shocks with DSC adjusters on this platform. The Dual Speed Compression knobs make it where you can easily dial in the low and high-speed compression. The low-speed adjuster removes unwanted sway, which can vary as you add and remove weight. The high-speed dial provides control for rapid suspension movement, such as hitting a large rock in the trail or speedbump you overlooked. This means you can dial in the Jeep for your driving style, current terrain, and provide the extra valving needed to control the nose-heavy Hemi JL.
Controlling Caster
Part of what makes the steering feel heavy is the fact that despite the two-inch lift, Jeep doesn’t put longer control arms on the Wrangler 392. This factory oversight places the castor around 4.3 degrees. An aftermarket set of lower control arms will provide you with increased castor, which will improve the steering responsiveness and lighten the feel. Control arms with an inward bend (similar to the factory) will provide great clearance for your front tires over straight arms.
Exhaust Tips
The exhaust sound on the 392 is fantastic, but the tips hang down too much for serious trail wheeling. An easy fix for trail days is to loosen the tips and rotate them upwards. When you are done with the trail, you can rotate them back using the existing alignment tabs to ensure you get them in the correct orientation.
More From Driving Line
- Watch our 392 build in action on our latest Inside Line video.
