Understanding Control Arms and Their Role in XJ Suspension

Control arms are the backbone of the Jeep Cherokee XJ’s front and rear suspension systems. These structural links connect the vehicle’s frame (or unibody, in the XJ’s case) to the axle, controlling the wheel’s path during suspension travel and steering. The XJ uses a four-link front suspension with two upper and two lower control arms, while the rear is a leaf-spring setup – though the rear upper control arms are actually part of the panhard rod and track bar system in some configurations, the core concept of arms managing axle location remains.

The geometry of these arms dictates caster, pinion angle, and roll center – all critical for both on-road handling and off-road articulation. OEM arms are designed around stock ride height and modest tire sizes. Once you lift an XJ or fit larger tires, the factory control arms often become a limiting factor for proper alignment and travel. Understanding the trade-offs between OEM replacements and aftermarket upgrades is essential for anyone maintaining or building an XJ.

OEM Control Arms – Specifications and Limitations

Original Equipment Manufacturer (OEM) control arms for the Jeep Cherokee XJ are produced by Mopar or licensed suppliers to the exact print used at the assembly line. These arms are stamped steel or cast steel, with rubber bushings pressed into the frame and axle ends. They are designed for a vehicle with no lift and factory tires.

Advantages of OEM Control Arms

  • Precision Fitment: Every mounting hole, bushing ID, and arm length matches the factory specifications. No grinding, welding, or drilling is needed.
  • Proven Durability: Millions of XJs left the factory with these arms; they handle daily driving, mild trails, and stock loads reliably for many years.
  • No NVH Increase: Rubber bushings absorb road vibration and noise effectively, delivering a quiet, comfortable ride.
  • Warranty Coverage: Mopar genuine parts come with a 12-month/unlimited-mileage warranty; some aftermarket suppliers also offer limited warranties, but OEM terms are straightforward.

Disadvantages of OEM Control Arms

  • High Cost per Arm: A single OEM lower control arm can cost $150–$250, while a set of four aftermarket arms may cost less total.
  • No Adjustability: Fixed length means you cannot correct caster or pinion angle after a lift. This leads to poor alignment, vibrations, and accelerated tire wear.
  • Weak Bushings: Factory rubber bushings are not designed for the increased leverage and misalignment that occur with lifted suspension. They tear, squeak, and fail prematurely.
  • No Performance Upgrade: OEM arms are exactly that – original equipment. They do not increase articulation, clearance, or strength beyond stock requirements.

Aftermarket Control Arms – A Broad Category

Aftermarket control arms cover everything from budget budget replacements to high-end race components. They differ in materials, bushing types, adjustability, and design philosophy. Understanding these categories helps you choose based on your specific needs – daily driving, rock crawling, or overlanding.

Types of Aftermarket Control Arms

  • Fixed Length: Some aftermarket manufacturers offer fixed arms that replicate OEM length but with stronger tubing and upgraded bushings. These are a good middle ground for mild lifts (1–2 inches) where additional caster correction isn’t critical.
  • Adjustable Lower or Upper Arms: These feature threaded ends or multiple mounting holes to fine-tune arm length. Adjustable upper arms are most effective for setting pinion angle, while adjustable lowers help with caster and wheelbase correction.
  • Complete Adjustable Sets: Replacing all four control arms with adjustable units gives maximum flexibility for lifts up to 6 inches or more. This is the standard choice for serious off-roaders.
  • Long Arm Kits: Not exactly control arms in the traditional sense – they replace the factory short arms with longer units that relocate the axle­mount pivot points. This dramatically improves articulation and ride quality over rough terrain, but requires cutting and welding.

Bushing Materials and Their Impact

The bushing is the most common failure point on any control arm. OEM rubber provides comfort but lacks durability under misalignment. Aftermarket options include:

  • Polyurethane: Firmer than rubber, resists tearing and oil exposure. Increases NVH noticeably. Requires occasional lubrication to prevent squeaking.
  • Duroflex or “Compliance” Bushings: A hybrid that offers more give than solid poly but still absorbs misalignment. Found on high-end brands like MetalCloak.
  • Heim Joints or Spherical Bearings: Unmatched articulation and zero flex for precise control. Transmit every road imperfection and require periodic cleaning and lubrication. Not street-friendly in many jurisdictions due to increased noise.
  • Johnny Joints (Currie Enterprises): A spherical bearing encased in a urethane race – combines the travel of a heim with reduced noise and vibration. Very popular in XJ aftermarket circles.

Material and Construction

OEM arms are stamped steel. Aftermarket arms often use:

  • DOM (Drawn Over Mandrel) Tubing: 1.25” to 1.75” diameter, 0.120 to 0.250 wall thickness. Common for budget to mid-range arms.
  • Chrome Moly (4130): Stronger and lighter than DOM, but more expensive. Used in competition-oriented arms.
  • Boxed Steel: Some brands form arms from plate steel welded into a box section – very strong but heavy.

Key Differences in Design and Performance

When you lay an OEM arm next to a quality aftermarket arm, several differences become apparent beyond just price.

Articulation and Flex

Stock control arms allow limited misalignment because rubber bushings bind when the arm rotates off its primary axis. Aftermarket arms with flex joints (Johnny Joints, heims, or even double-adjustable poly bushings) allow the arm to rotate freely. This directly translates to more wheel travel. For example, a stock XJ might achieve 8 inches of front wheel travel; a properly built long-arm system can exceed 14 inches. Even short-arm aftermarket kits often gain 2–3 inches of useable travel by replacing bushings.

Ride Quality and NVH

Ride quality is a trade-off. OEM arms with fresh rubber bushings are soft and quiet. Polyurethane bushings often increase road noise inside the cabin and transmit small bumps harshly. However, well-engineered aftermarket arms with compliance-style bushings (like MetalCloak’s Duroflex) can actually improve ride quality by reducing binding in the suspension – the arm moves more freely, so the suspension works better over small bumps. Spherical ends remain harsh; they are not recommended for daily drivers unless you are building a dedicated off-road rig.

Durability and Corrosion Resistance

OEM arms are coated in black paint that chips easily, leading to rust. Aftermarket arms often come with powder coating, zinc plating, or even stainless steel components. The welds on reputable aftermarket arms are typically stronger than the factory spot welds. Heim joints will corrode if not maintained; Johnny Joints are more corrosion-resistant because the steel ball is heat-treated and the urethane race protects it. Core4x4 arms use a hybrid bushing with a zinc-plated socket that resists rust well.

Not all aftermarket brands are equal. Here are four major players in the XJ market, each with a distinct philosophy.

Rough Country

Rough Country is the budget king. Their adjustable lower and upper control arms use rubber bushings in the frame side and poly in the axle side. Pricing is low – about $150 for a set of four lowers. Finish is powder coat, and the arms are 2x0.120 wall DOM tubing. They work well for mild lifts (3–4 inches) and light off-road use. The primary downside is bushing longevity: poly dries out after a few years, and the rubber ends can tear under extreme articulation.

Rubicon Express (RE)

RE is a classic XJ brand whose arms use a patented “Super-Flex” joint – a spherical ball in a urethane race similar to a Johnny Joint but with a different design. RE arms are stronger than Rough Country (thicker tubing and better welds) and deliver excellent articulation. They are more expensive but offer a good balance of performance and street manners. The Super-Flex joint tends to wear faster than a true Johnny Joint but can be rebuilt.

MetalCloak

MetalCloak’s Game-Changer line uses their proprietary Duroflex bushings, which behave like rubber in terms of noise and vibration but handle extreme misalignment without tearing. The arms are made from 2x0.250 wall DOM tubing with welded clevises. They are the premium choice for serious off-roaders who still drive their XJ on the street. The Duroflex joint is rebuildable and outlasts most competitors. Expect to pay $500–$800 for a full set of four adjustable arms.

Core4x4

Core4x4 offers a unique “Tiered” system – Tier 1 uses rubber bushings (stock replacement), Tier 2 uses poly, Tier 3 uses their “Flex Joint” (a spherical bearing with urethane cup). All arms are made from 1.75x0.120 wall DOM and are fully adjustable. The modular bushing system allows you to upgrade bushings later without buying new arms. This versatility makes Core4x4 popular among owners who want to start with a street-friendly setup and later convert to a flex joint for off-road use.

Installation Considerations

Installing control arms is a straightforward job for a skilled home mechanic, but there are nuances that can turn it into a nightmare if ignored.

Tools and Difficulty

Basic tools: floor jack, jack stands, wrenches, socket set, breaker bar, torque wrench, and penetrating oil. You will also need a press or a ball joint press for removing and installing bushings – but if you buy arms with pre-installed bushings, you avoid that step. Adjustable arms require setting the length before installation; a tape measure and angle finder are helpful. Plan for a weekend day; the job usually takes 4–8 hours for all four arms, depending on rust.

Alignment After Installation

Changing control arm lengths alters caster, pinion angle, and toe. You must get a professional alignment afterward. A shop that knows lifted XJs will set caster to 5–7 degrees, pinion angle within 1 degree of the driveshaft centerline, and toe to 1/8” in. Without proper alignment, you risk vibrations, wandering steering, and premature tire wear.

In many states and countries, modifying the suspension beyond a certain height is illegal for road use. Control arm replacement itself is not regulated, but if adjustable arms allow you to lift beyond legal limits, you may fail inspection. Additionally, aftermarket arms with heim joints or poly bushings may not pass noise or safety inspections in some jurisdictions. Check local laws before installing.

When to Choose OEM vs. Aftermarket

The choice ultimately comes down to your XJ’s intended use and your budget.

  • Choose OEM if: You own a stock-height, low-mileage XJ that you use only for daily commuting and occasional highway trips. You want worry-free fitment and are willing to pay more for convenience. Your lift height is 0–1 inches, and you have no caster complaints.
  • Choose Aftermarket Fixed-Length with Rubber Bushings if: You need to replace worn arms on a mild lift (1–2 inches) and want an upgrade in strength without modifying geometry. Brands like Quadratec’s house brand offer this at a fair price.
  • Choose Adjustable Arms if: Your XJ has 3+ inches of lift, or you want to optimize caster and pinion angle. You plan on off-roading regularly. You are willing to invest in quality components like MetalCloak or Core4x4 to avoid NVH issues. Read this forum guide to understand geometry before buying.
  • Choose Long Arms if: You are building a dedicated rock crawler or buggy-style XJ with 6+ inches of lift. Long arms transform the ride and articulation but require significant cutting, welding, and cost.

Conclusion

OEM control arms are a safe, proven choice for a stock or near-stock Jeep Cherokee XJ, offering easy installation and a comfortable ride at a premium price. Aftermarket arms, however, solve the fundamental limitations of the factory design – lack of adjustability, weak bushings, and insufficient strength for lifted operation. By choosing the right aftermarket brand and bushing type, you can dramatically improve your XJ’s off-road capability while maintaining acceptable on-road manners.

No single “best” option exists; the right control arms depend on your lift height, driving habits, and budget. Invest in quality bushings, get a proper alignment, and your XJ will reward you with years of reliable service off the beaten path.