From YJ to TJ: The Evolution of the Jeep Wrangler

Riding on the heels of the successful transition from the CJ series to the Wrangler YJ, Jeep started development of its successor in 1990. In its initial design phases in the Jeep-Truck Engineering Pre-Program at Chrysler, several test-bed mules based on the YJ were produced between 1990 and 1993 with different mechanical features. In 1993, Chrysler executives approved a $260 million budget to begin the TJ Development Program.

During the first three mule years, a particular variant of the mules designed by Michael Santoro was chosen by Lee Iacocca and other executive management as the design to be moved forward. In May of 1993, the final TJ design had engineering and supplier backing and the final production design was frozen 32 months before initial mass assembly.

Mule verification of prototypes began in early 1994 and was tested through late 1995. With the final prototypes being built with production bodies, Chrysler ceased production of the YJ in December 1995 and began the re-tooling process of the Toledo plant for the production launch of the TJ in January 1996.

On January 2, 1996, the TJ was unveiled to the public at that year’s Detroit International Auto Show as a ‘97 model and was met with acclaim. Gone were the older leaf springs, and the platform was updated with the new coil spring setup that was initially developed for the XJ Cherokee. The system was modified and used in the rear suspension as well, coining the name for the system as ‘Quadra-Coil’ which is still used today in the new JL platform. This move to coil springs resulted in better ride handling and articulation off road. Power came from the returning 4.0L AMC 242 inline-six that was also being used in the Cherokee and Grand Cherokee. A smaller power plant option was available in the form of the 2.5L AMC 150 inline-four. Axles came in the form of a Dana 30 front, and a standard Dana 35 in the rear with an optional Dana 44. Transmissions were also held over in the form of a five-speed manual transmission and a four-speed automatic. The TJ is notable as having the last of AMC hold-over parts of any Chrysler vehicle.

For the 1999 model year, the fuel tank was standardized to 19 gallons, and various modifications and updates were issued going forward, most notably in 2003 when the Rubicon model was introduced. The Rubicon featured front and rear Dana 44 axles, a NV241OR transfer case with a 4:1 low range, front and rear differential air-lockers, shorter 4.11 gearing and 31-inch Goodyear MT/R tires. In 2003, the interior was also updated and the external side mirrors were changed from metal-cased to plastic. Also in 2003, the 2.5L inline four engine was replaced by the more modern Chrysler 2.4L DOHC inline-four that was used in the Dodge Neon, and the 4.0L received coil-on-plug ignition, replacing the distributor.

The final feather in the TJ’s hat was unveiled in April 2004, with the introduction of the Wrangler Unlimited. The Unlimited (LJ) was essentially a TJ that had been stretched 10 inches at the wheelbase (15 inches total), and the tub was lengthened slightly behind the rear axle as well. The LJ came standard with a Dana 44 rear axle and a Dana 30 front. In late 2004, the Rubicon Unlimited was introduced that carried over all of the features from the standard Rubicon, but with the Unlimited’s longer wheelbase and body.

For the final two years of production, the five-speed manual transmission was replaced by a six-speed with a low first gear and the interior received another update. Production ended in mid-2006 and was replaced by the two and four door variants of the new Wrangler JK. Along with the end of production of the TJ, the Toledo plant, where all variations of CJ and Wrangler’s had been built since World War II, was torn down—with Chrysler leaving a sole smoke stack surviving from the plant with the letters OVERLAND bricked into its face.