Skyjacker YJ40RSB Sport Series Rear Leaf Spring 4in Lift 1987-1995 Wrangler YJ

Vehicle Fitment

• 1987-1995 Jeep Wrangler YJ - all trims, 4WD, rear axle

Fitment Notes

• Rear axle only - the YJ40RSB is a rear spring; a complete rear axle lift requires two springs (one per side); springs are sold individually - order two for a full rear set
• 4-inch lift specification - this spring is designed for a 4-inch lift application; pairing it with front springs of a different lift height will result in uneven ride height; for a complete 4-inch lift system, use with matched front springs of the same lift specification
• Bushings not included - the spring is sold without end-eye bushings; Skyjacker's polyurethane replacement bushing kit SE4YJ is compatible with the YJ40RSB and is recommended for installation with new springs; stock rubber bushings can be reused if they are in serviceable condition
• Compatible with all 1987-1995 YJ variants - the rear spring mounting geometry is consistent across all YJ Wrangler production years and trim levels; the YJ40RSB fits both the base and Sahara/Islander/Renegade and other trim variants
• Limited Lifetime Warranty - Skyjacker covers all leaf springs with a limited lifetime warranty to the original purchaser for the length of ownership of the vehicle on which the springs were originally installed

Features

• Shot-peened leaf construction - each individual leaf in the spring pack is shot-peened before assembly: a process in which hardened steel pellets are projected at high velocity at the surface of the spring steel; the impact of each pellet plastically deforms a small area of the surface, inducing a layer of compressive residual stress into the steel; fatigue cracks in metal almost always initiate and propagate from the surface under tensile stress; the compressive stress layer introduced by shot peening opposes the tensile stress that would otherwise be generated under load, dramatically increasing the number of load cycles the spring can endure before fatigue failure; without shot peening, achieving the combination of maximum wheel travel and service life in a thinner, more flexible leaf profile would not be possible; shot peening allows Skyjacker to build a spring that flexes more and rides better while lasting longer than a non-peened spring of equivalent dimensions
• Full-length tapered leaf profiles - each leaf is tapered over its entire length rather than being a constant cross-section bar; the leaves are thickest at the center where bending stress is greatest and progressively thinner toward the ends where the spring must flex the most; this taper serves two purposes: it distributes the bending load more evenly across the length of the leaf rather than concentrating stress at a few discrete points, and it reduces the tendency of the edge of one leaf to bite into the surface of the leaf above it during articulation; leaf-on-leaf digging (which occurs with blunt, constant-thickness leaf ends) generates friction, noise, and surface damage that degrades spring performance and life; the tapered profile nearly eliminates this phenomenon, producing smoother, quieter articulation over the spring's service life
• Bolt-style floating spring clips - the leaves of the YJ40RSB are held together by bolt-on, floating spring clips rather than the cinch or crimp-style bend clips used in many OEM and aftermarket springs; a cinch-style clip is bent tightly over the spring pack and contacts the outer leaves with significant clamping force; this lateral pressure adds friction to the leaf interfaces and resists the individual leaves from sliding relative to each other as the spring articulates, increasing spring rate and degrading ride quality; Skyjacker's bolt-on clips are fastened through the spring pack but are sized to cradle the leaves without applying lateral clamping pressure; the leaves remain free to slide slightly relative to each other during articulation, as a leaf spring is designed to work, eliminating clip-induced friction and allowing the full designed spring rate to manifest in actual use
• American steel construction - the spring steel for the YJ40RSB is sourced from US mills; spring steel for off-road leaf spring applications must meet specific chemistry (typically a silicon-manganese or chromium-vanadium steel grade) and heat treatment specifications that govern strength, fatigue resistance, and elasticity; domestic steel production provides material traceability and consistency important for safety-critical suspension components
• Black corrosion-resistant coating - the Sport Series designation includes a black powdercoat or corrosion-resistant finish on the spring assembly, providing protection against the road grime, water, mud, and UV exposure inherent in Wrangler operation; the coating also provides a uniform appearance suitable for the visible underside of a lifted Jeep
• Built-in 4-inch lift geometry - the spring's arc (free arch) is engineered to produce a 4-inch lift at the rear axle relative to the factory ride height when installed at the vehicle's unladen static position; no lift blocks or spacers are required to achieve the stated lift height

Specifications

• Part Number: YJ40RSB
• Brand: Skyjacker Suspensions
• Product: Sport Series Rear Lift Leaf Spring
• Lift Height: 4 inches
• Position: Rear
• Application: 1987-1995 Jeep Wrangler YJ - all trims, 4WD
• Construction: Shot-peened, tapered American steel with bolt-style floating spring clips
• Finish: Black corrosion-resistant coating
• Bushings Included: No - order SE4YJ separately
• Quantity: Sold individually (1 spring per order; order 2 for complete rear axle)
• Warranty: Limited Lifetime (original purchaser, for length of vehicle ownership)

Included Components

• 1x Skyjacker YJ40RSB Sport Series Rear Leaf Spring (4 in. lift)

Product Description

The Skyjacker YJ40RSB is the Sport Series 4-inch rear lift leaf spring for the 1987-1995 Jeep Wrangler YJ, sold individually. It is a direct replacement rear spring that replaces the factory YJ rear leaf spring with a new assembly engineered for a 4-inch lift height, built from shot-peened American steel with tapered leaf profiles and bolt-style floating spring clips.

The shot peening process is the central performance element of Skyjacker's spring design: each leaf is individually processed before assembly, compressing the steel surface and creating a residual compressive stress layer that resists the fatigue crack initiation that terminates conventional spring life. This allows Skyjacker to build a spring with the thinner, more flexible cross-section geometry needed for maximum wheel travel and ride quality without shortening the spring's service life. The tapered leaf ends and bolt-style clips address the other two chronic problems of leaf spring design - leaf-on-leaf digging and clip-induced friction - producing a spring that articulates smoothly and quietly throughout its range of travel.

Sold individually; order two for a complete rear axle set. Bushings are not included - Skyjacker's SE4YJ polyurethane bushing kit is compatible. For front springs to complete a 4-inch system, pair with the appropriate Skyjacker YJ 4-inch front spring. Limited Lifetime Warranty to the original purchaser.