Jeep Wrangler Lift Kit: All-Around YJ UnderpinningsPosted in How To: Suspension Brakes on October 1, 2012 Comment (0)
The ’87-’95 Jeep Wrangler YJs are now one of the best values in wheeling. They’re incredibly affordable in decent condition, and their aftermarket is still active. (On the flipside, the recession caused many CJ part numbers to disappear—as well as many of the yuppies who were originally attracted to the YJ.)
For extreme trail-only use, a ’97-’06 TJ is probably a better Jeep platform. For a budget street/trail Jeep, though, the YJ is tough to beat.
Spring-under leaf lifts are a high-value YJ upgrade since they’re easy enough to do at home. YJ springs can be sourced dirt-cheap through many mail-order sources, although some kits might not include all the necessary components to cure rear driveshaft vibration. For YJs, this includes transfer case shims to eliminate rear driveshaft vibration. (At under 4 inches of lift, the shims might not be necessary if the NP231 has a slip-yoke eliminator kit and an aftermarket rear driveshaft with CV joints.)
Superlift actually offers three 31⁄2-inch kits for fitting 33s, keeping YJs streetable while improving off-road clearance and articulation. The “soft” spring-rate Superide kit is intended for four-bangers/soft tops, while the “stiff” HD kit is engineered for YJs that have six- or eight-cylinder engines, winch bumpers, and hardtops. In the middle ratewise is the premium 31⁄2-inch kit from the company’s trail-oriented Black Diamond division. Besides having different spring rates, the Black Diamond leaves feature tapered plates and Teflon antifriction pads for easier articulation. Details that improve durability include shot-peened leaves, military double-wrapped spring eyes, flat pad seats (which reduce spring sag and stress), and urethane spring eyes.
We went with the stiffer HD kit because our particular YJ has the 4.0L engine and some accessories. Stiffer springs also settle and sag less over time.
Superlift doesn’t publish spring rates for a few reasons, first and foremost being that leaf spring rates aren’t truly linear, and the rating depends on whether the rate per inch is determined from the free/unladen position or the curb/loaded position. If measured from curb weight, any manufacturer’s weight rating likely wouldn’t reflect a modified 4x4’s actual curb weight.
This job was a budget rehab of a YJ that previously had an experimental monoleaf suspension. The Jeep already had a fully functional aftermarket steering stabilizer and sway bar disconnects; both are available from Superlift.
Superlift also offers the NP231 slip-yoke eliminator kit, upgraded DOT-compliant braided steel brake hoses, and TruSpeed speed recalibration module (for ’92-’06 YJs and TJs). This install-it-yourself kit fits up to 33x12.50 tires. Stock wheels will clear; aftermarket recommendations are minimum 15-inch diameter, maximum 8-inch width, and between 31⁄4 and 4 inches of backspacing.
Devoting five or so hours in your driveway and a few hundred bucks can give YJs a new street/trail attitude. Ridewise, the “stiff’ Superlift springs are surprisingly soft, having a comparable road ride to the funky monoleaves they replaced.