Theyre out there, the YJ haters. Weve even been called owners of the W word as an attempted insult. Spit on em. Truth is, YJs can cost less than a CJ-7, they have better frames, theyre lighter, theyre more plentiful, and most of them have fuel-injection. You may not be able to fit 32-inch tires on a stock YJ and the transfer case and transmission may be made out of old Budweiser cans but thats a bonus when youre building a nimble lightweight Jeep. Weve been known to try and get under peoples skin and what better way to do so than to build up a really capable square-headlight YJ thats hard to hate. Wed start with a 91-96 YJ with a 2.5L four-cylinder and multi-port fuel-injection. All YJ four-cylinders have fuel-injection but the later 2.5Ls have a little more horsepower. The four-banger would provide added insult to any cranky CJ owners but still provide plenty of power with the right gearing.
Chassis & Driveline
We would keep the frame stock but run a high-clearance skidplate. The Wrangler frames are pretty strong as is. Wed replace the disconnect Dana 30 front axle with an XJ high-pinion Dana 30 and stuff it with 4.88 gears, 297-jointed alloy axles, and a locker. The XJ axle is lighter, less complex, and has the same compact but strong ring-and-pinion as the YJ Dana 30. Out back wed throw in a high-pinion Dana 44 with 4.88s, a locker, and 33-spline axles from Drivetrain Direct. Wed keep the suspension simple and find front 2 ½-inch lift springs with the lightest spring rate available and hang them off of a shackle-reversal kit that provides about 1½ inches of lift. In the rear wed find the softest 3 ½-inch springs and mount them up with boomerang shackles. Wed keep the 2.5L, install headers, a complete exhaust system, and an open-element air filter. The original AX5 would stay but the 231 would get swapped in favor of an Atlas II with the 4.3:1 low-range gears. This combo would provide a crawl ratio of about 80:1. It isnt quite as low as we would like but wed make due or move the engine forward 6-8 inches and install a Klune-V with a 2.72:1 ratio. Then wed be down to 217:1, which is probably too low.
Body & Interior
The factory tub stays but would receive a set of rocker guards, a 1- or 2-inch body lift, and some fender trimming to help clear the 35-inch tires. Wed run complete soft doors and a soft top for weight savings. The front inner fenders would be removed for the same reason and the fenders and hood would be replaced with fiberglass, preferably a one-piece unit. Wed remove the factory rollbar and build a complete cage using 1 ¾-inch .120-wall DOM tubing in the main bars, mount it to the frame, and incorporate seat mounts bolted to comfy low-back buckets. The rear seat would be removed and replaced with a spare tire mounted to the floor. Everything else would remain mostly stock, including the A/C and heater for all-weather wheeling.
Wheels & Tires
Wed run lightweight 35-inch mud tires with an aggressive tread pattern and strong sidewalls. The 35s would be mounted to lightweight 15x8 aluminum wheels with bead locks. Nothing particularly special here but lightweight is key since the four-banger isnt exactly overflowing with torque. Excessive rotating weight is a performance killer.
Good, Bad, & What It's For
The advantage the YJ has over earlier Jeep models is that almost everything could be bolt-on. The four-banger is probably a joke if you live in mountainous areas and wanted to use it as a daily driver or if you like to blast over huge dunes. But with the right gearing the four would be perfect for high-revving short bursts and crawling trail duty.