RockKrawler's 4.5" X Factor mid-arm kit uses longer-than-stock lower arms and triple-rate coils, splitting the difference between short arm and full long arm.
RockKrawler's 4.5" X Factor for the XJ is a mid-arm kit — the front lower control arms are longer than stock but shorter than a full long-arm conversion, and they bolt to a slightly relocated crossmember. This recovers most of the geometry benefit of long arm (better caster, less pinion-angle change under flex) without the install complexity. Triple-rate front coils give an exceptional ride for the height; the kit ships with RK 2.0 shocks (Fox or King upgrades available).
Included: triple-rate front coils, full rear leaf pack, RK 2.0 emulsion shocks, X Factor front lower arms, adjustable front and rear track bars, brake line drops, transfer case drop, and steering stabilizer. SYE/CV not included. Expect $2200-2800 for the kit.
The X Factor is regarded as one of the best-riding 4.5" kits on the XJ platform. Its main weakness is cost — by the time you add SYE/CV, caster correction, and shocks upgrades, the X Factor is in the $3000+ range, which is real long-arm territory.
| Part | Vendor | Est. price |
|---|---|---|
| RockKrawler XJ 4.5" X Factor Kit | RockKrawler | ~$2400 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.