40-inch-tired, 1-ton TJ
Trent Fabrication of Sparks, Nevada, produces some of the most capable rock buggies around. That being the case, it was no surprise when Trent Fab owner Derek Trent took the torch to his wife’s ’04 TJ Rubicon. Lisa Trent already had 37-inch-tall tires and a long-arm suspension on her Rubicon, but instead of getting an engagement ring, she got engagement beadlock rings. Derek performed a slew of upgrades that provide the TJ with more strength, ground clearance, and articulation on the trail. The Trent couple recently took the opportunity to show off the Jeep’s capabilities at Off Road Innovations of Reno’s new Giant’s Throne OHV Park. Unlike the purpose-built buggies, this Jeep is still street legal and the cage fits under the factory hard top. This allows the couple to use the Jeep for snow bashing during the brutal Tahoe winters, and it can still be legally driven on the street to access the nearby Rubicon Trail.
Much of the factory frame still remains under Lisa’s Jeep, but the front framehorns were replaced in front of the motor mounts with stacked 1.75-inch, 0.156-wall DOM tubing when the wheelbase was stretched. Moving the front axle forward on a TJ is a great way to increase the approach angle and wheelbase, but it creates interference issues with the steering box and track bar locations on the frame. Derek took the opportunity to address those issues when he pushed the axle forward for an approach angle of more than 90 degrees. A PSC steering box is located on a custom frame mount and is tapped to pressurize the hydraulic-assist steering ram.
The front suspension uses custom radius arms constructed from 2-inch, 0.250-wall tubing fitted with QA1 rod ends. A 1.25-inch cold-rolled, solid-steel track bar mirrors the drag link geometry to ensure no bumpsteer. The small diameter was necessary for the tight clearances under the Jeep, and similar 1.5-inch cold-rolled, solid-steel was used for both the tie rod and drag link for the same reason. Front and rear, 14-inch-travel 2.0 Fox remote-reservoir coilovers are used. The front pair is mounted on a custom engine cage and the rears are Frenched into the frame with Trent Fabrication tubular mounts. The rear suspension is a triangulated four-link that eliminates the need for a track bar. The lower links are constructed of 2-inch, 0.375-wall tubing while the uppers were fabricated from 1.75-inch, 0.250-wall tubing. A Rock Equipment sway bar is used on the rear axle to provide stability and balance with the coilover suspension.
The suspension clears 40x13.50R17 Goodyear MT/Rs wrapped around Allied Raceline Monster beadlocks. The MT/Rs are relatively light and narrow for a 40-inch-tall tire, making them a great choice for a vehicle that still sees street use. Keeping with the weight-conscious theme, the Allied Raceline beadlocks are built from high-quality cast aluminum, so they’re much lighter than steel beadlocks. A PSC steering box, pump, and hydraulic-assist ram turn the big tires, even when they are bound up in the rocks. The hydraulic assist retains a mechanical linkage and provides much better feedback at speed than a full-hydraulic steering system. When the frame was stretched, the steering box was rotated so that the pitman arm is four inches further forward than stock.
The factory 4.0L engine is still in place and backed by the factory 42RLE automatic transmission. This was the first overdrive automatic transmission used in a short-wheelbase Jeep, and it has proven to be strong and reliable, although it does sap power from the six-cylinder engine. Beyond the transmission, an Advance Adapters Atlas II transfer case with a 4.3:1 low range replaced the factory NP241OR Rocktrac transfer case. Why replace the already outstanding 4:1 Rubicon T- case? The Atlas II is gear-driven and allows the use of front-wheel drive for tighter maneuvers on technical obstacles. The turning radius is further enhanced by cutting brakes plumbed to each rear corner.
With 40-inch-tall tires, only 1-ton axles were acceptable. The Dana 60 axles were narrowed to 65 inches and filled with 5.13 Sierra gears and ARB Air Lockers before getting capped off with Rockcrusher covers. The front axle is from a ’92 Ford F-350, before Ford went to the goofy metric eight-lug bolt pattern, and uses Superior 35-spline chromoly axleshafts and CTM U-joints. The rear axle was sourced from a Ford van and has a smooth bottom on the housing and equal-length shafts to minimize the number of spares that need to be carried on the trail. The front axle runs the stock 1-ton calipers, while the rear axle uses 1⁄2-ton Chevy calipers in conjunction with a 1-ton Dodge master cylinder bolted to the factory TJ brake booster.