70-74 / E Body / Independent Rear Suspension

Description

> Description Delivering unmatched ride quality, superior grip, and modern handling for your 70-74 E-Body (Challenger & Cuda) , the Speedtech Independent Rear Suspension (IRS) transforms your muscle car into a precision-handling machine. Designed with optimized geometry, high-strength materials, and track-tested performance, this system gives you the confidence to carve corners, launch harder, and enjoy a smooth ride—all in one package. With up to 315mm tire clearance, precise camber control, and full coilover adjustability, this bolt-in IRS brings next-level performance to the street or the track—without major chassis modification. MODERN RIDE QUALITY, MAXIMUM GRIP Independent suspension arms allow each rear wheel to react individually to the road, maintaining optimal tire contact and drastically improving both cornering and comfort. The result? A compliant, composed ride with relentless grip and balance. FULLY TUNABLE PERFORMANCE Double-adjustable QA1 or JRi coilovers paired with optimized motion ratios let you dial in ride height, rebound, and compression to match your driving style—whether you’re cruising, autocrossing, or road racing. WIDE TIRE FITMENT, ZERO COMPROMISE This system is engineered for aggressive setups—fit up to a 315/30/18 rear tire with full suspension articulation. Built-in camber and toe adjustability help you fine-tune alignment for the perfect stance and optimal contact patch. (With mini-tubbed applications, a 355mm tire width has been used) TRACK-TESTED STRENGTH Using Strenx® high-strength steel, the IRS cradle and control arms maintain incredible rigidity while reducing weight. Precision TIG-welded components and reinforced pickup points deliver long-term durability under high-stress conditions. WELD-IN INSTALLATION This IRS is a true re-design to the rear end suspension and floor/housing. The entire assembly is engineered to line up within stock frame rails. With our over-head design as a featured element in the trunk space, it retains usable interior trunk space, making it ideal for builds where drivability and refinement are just as important as performance. PROUDLY BUILT IN THE USA Crafted with pride in the USA from premium materials, this system is built to handle serious performance demands without sacrificing ride quality or reliability. Tech Info ExtReme IRS Install ExtReme IRS Sheet Metal Guide Close × FREQUENTLY ASKED QUESTIONS (FAQ’s) IS THE SPEEDTECH IRS SYSTEM GOOD FOR STREET AND TRACK USE? Yes. The Speedtech IRS system is designed to deliver a balance of ride quality and performance, making it ideal for street driving, autocross, and track days. It provides improved stability, traction, and overall drivability compared to traditional solid axle setups. WHAT SIZE TIRES CAN I RUN WITH THE SPEEDTECH IRS? The IRS system allows for wide rear tire fitment, supporting up to 355-width tires (depending on vehicle and wheel specifications), giving you maximum grip and performance. HOW DOES THE IRS SYSTEM INSTALL? The IRS system is designed to integrate with Speedtech chassis systems and can also be installed into select factory frames with proper fabrication and installation work. It is not a direct bolt-in upgrade. Installation requires chassis modifications, fabrication, and precise setup to properly mount the independent rear suspension components in place of the factory solid rear axle. WHAT MAKES SPEEDTECH’S IRS DIFFERENT FROM OTHER SYSTEMS? The system features fully adjustable camber, caster, and toe, allowing precise tuning for different driving conditions. Its geometry is engineered to improve traction, reduce squat, and maintain tire contact through corners. WHAT’S INCLUDED WITH THE SPEEDTECH IRS SYSTEM? Rear Upper and Lower Control Arms Forged Spindles with C7 Hubs CV Axles (rated at 1,200 HP with upgrade options for 1,800) Aluminum 9” Housing and Stub Axles Center Section Rear Sway Bar and Linkage Mounting Cradle / Structure Applicable Hardware Related Products Quick view 1970-1974 Mopar E-Body Torque Arm Rear Suspension View Product Quick view 1970-1974 Mopar E-Body Extreme Subframe View Product Quick view 1970-1981 GM F-Body Independent Rear Suspension View Product Quick view