Independent Rear Suspension 70-74 Cuda/Challenger


Independent Rear Suspension (IRS) is the ultimate expression Pro Touring to make your classic car drive like a modern luxury sport touring car. If you are not familiar with the term Pro Touring consider the following.  Pony cars of the 60s & 70s were manufactured to perform well in a one specific narrow driving circumstance, straight-line acceleration.  Pro Touring is defined as a classic America muscle car with enhanced capability for braking and cornering.  The essence of Pro Touring is a great handling muscle car that is fun to drive on the street and is also competent on a road-course. Speedtech Performance offer our award winning IRS design for a wide range of vehicles.


  • 55.5″ hub to hub
  • Speedtech Performance exclusive forged ExtReme spindle
  • Replace rear straight axle with award winning Independent rear Suspension
  • increased motion ration allows for lower spring rates
  • Improved comfort and performance
  • Better tire compliance with road surface
  • Two Versions – Low Mount Shock and High Mount Shock (Cantilevered/Rocker Arm)
  • Great for frequently driven cars and cars used to travel in
  • Built to handle up to 1,200 HP with upgrades available to reach 1,800 HP
  • C7 maintenance free sealed double bearing with C7 Hub 12 x 1.5 studs that match the ExtReme front
  • Fully adjustable rear alignment Camber, Toe and both corse and fine tuning for Bump Steer
  • Reduction of the all important unsprung weight allows better shock control


  • Speedtech Performance IRS Rear cradle/subframe
  • Billet aluminum High Mount actuating rocker arms (high mount system only)
  • Speedtech Performance exclusive ExtReme forged spindles
  • 35 Spline Inner Stub Axles
  • Outer C7 33 spline stub axles
  • 33 spline EMPI 934 CV Joints
  • Hy Tuff 1/2 Shaft Axles
  • Your choice of gears
  • Dutchman Aluminum Housing
  • JRI Speedtech valved single adjustable coil over shocks with JRi springs
  • All IRS packages come standard with E Brake

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Installation Instructions