Adding Inches To A TJ Wheelbase For Smoother Street And Trail Performance
Some of the most important geometric elements of a four-wheel-drive vehicle are approach and departure angles, as well as ramp breakover angle-the angle that's measured by drawing a straight line from the trailing edge of the front tires or from the leading edge of the rear tires in order to a location on the frame that's midway between the two points. With high ground clearance and relatively large tires, a typical Jeep has a tall breakover angle and short overhangs, and is less prone to hanging up and dragging its bumpers and undercarriage over obstacles on the trail. However, that nimbleness on narrow, rocky trails comes at the price of a higher center of gravity which can affect performance on steep hillclimbs and descents, and which can also result in a tippy and wallowy-feeling ride on pavement. Also, a rig with a relatively tall breakover angle and a higher center of gravity can be more prone to driveline and steering angularity problems, particularly if larger-than-stock tires are installed.
On the other hand, a vehicle with a longer wheelbase, and hence a lower breakover angle, is often more able to straddle steep rocky hillclimbs and downhills than a shorter-wheelbase rig, and its lower center of gravity (assuming tire sizes are equal) results in a smoother ride on pavement and graded roads. Steering and driveshaft angularity problems are minimized, too, though new drivelines, U-joints, and extended-length steering and brake-line components would obviously need to be ordered if you stretch your wheelbase an inordinate amount. If your trail Jeep is also your daily driver, though, a longer wheelbase can be a modification worth looking into.
That is why we decided to investigate the growing trend associated with wheelbase extensions for Jeep TJs. Everyone knows that a longer wheelbase can improve a vehicle's ability to straddle ruts and climb steep hills, but given the price of such modifications, it is often difficult to quantify a return on the investment. We looked at three different wheelbase stretch kits available today and studied the pros and cons to see which kit presented the best value for the dollar spent. We picked the one kit we thought best demonstrated the benefits of such a conversion and installed it on a friend's daily driver, a '97 TJ. Our plan was simple: evaluate the kit and take notes on what it was actually like to live with for a typical year. Our results may surprise you.
The Lowdown on How It's Done
Each of the three TJ stretch kits we studied achieved the same basic goal of lengthening the wheelbase. However, one kit in particular outshined the others in terms of component quality, fit and finish, and completeness. Satisfied with our investigative work, we requested the Stealth Stretch manufactured by PureJeep of Bakersfield, California. PureJeep's system impressed us because of several details that were not addressed in the other kits.
The price of each kit was also taken into consideration, and the Stealth Stretch had a clear advantage over others we looked at. We liked the fact that the entire conversion comes from one company, and the kit includes everything needed to complete the conversion except for lengthening the rear driveline. Also, due to the nature of the kit, we figured to improve our Jeep's departure angle-without a lift or bigger tires-while maintaining front approach angle and gaining the benefits of a longer wheelbase in the process. To make the project happen, we enlisted the Jeep specialists of JC Fab in Sylmar, California, to ensure that each component was installed as intended.
The kit requires permanent modifications to the vehicle's body, so it goes without saying that mechanical experience is a key to the project's success. Additionally, the setup required revisions to the rear suspension, so it's good to have a basic understanding of link suspension arrangements. JC Fab's owner Jim Cox was more than qualified for the conversion, thanks to his extensive background in high-end Jeep buildups and custom fabrication.
This photo shows all of the rear suspension-related items included with the Stealth Stretch conversion. The PureJeep system uses suspension components from its sister company Full-Traction Suspension. Full-Traction has been building three-link Jeep suspension systems for years, so combining all of the proven parts into one complete system is a natural fit. The completely adjustable three-link setup shown employs a stout upper V-bar and lower adjustable control arms to locate the axle. This setup allows you to ditch the rear track bar, thus changing the way the rear axle and suspension cycle. Instead of the rear axle moving side-to-side in relation to the chassis throughout the range of motion, the new arrangement keeps the pumpkin centered under the vehicle as the suspension reacts to terrain inputs. Fully bolt-on, the kit also includes laser-cut coil-spring frame relocation brackets with retainers to prevent coil movement and noise under extreme articulation.