Torque Arm Kit V.14


The GR40 TorqueArm is the heart of the suspension system.

TorqueArm Kit, Gen 14 Severe Duty. 79-04


The GR40 TorqueArm is the heart of the Rear suspension system. 

Griggs Racing was the first to fit TorqueArms® to Mustangs and has done so since 1979. As with all our products we continually evaluate the needs of our customers, and upgrade the product as vehicle weight, power, brake and tire loads have increased, while endeavoring to keep cost of production of the best possible product within reach. And at the same time, continuing our policy of a lifetime warranty against breakage of most of our parts.

Our original production TorqueArm® for Mustangs with 8.8 inch rear axles were first offered in 1979 to accommodate the needs of drivers with Mustangs making 3-400 horsepower with drum rear brakes, and on tires of the day. Today, many of our customers are driving cars topping 2 tons, with tires producing 3 times the grip as in 1979, and with power adders as much as 1300 or more horsepower on which our newest design TorqueArm® is proving to be the standard of excellence. So we have discontinued all previous designs. (Legacy TorqueArms® are still available by special order).

Quick Facts

  • Improved strength. FEA and race tested.
  • Eliminates potential shuffle of differential cover precluding gear oil seepage/leaks.
  • Reduced resonance for quieter operation than any other unit on the market.
  • Provides easier TorqueArm® removal and re-installation during rear axle maintenance.
  • Mounts independent of Watts linkage.
  • Can be used with ANY differential cover or Girdle. (Some covers may require drilling of two 3/8 inch dowelpin holes. Tools available.)
  • Adjustable Pinion Angle.
  • Now only one part number per genre of GR40 or GR350 systems, each rated at 1300 hp capacity:
  • And the only TorqueArm on the market with a lifetime guarantee**.

How does it work? 

Basically a TorqueArm is one long traction bar that applies loads consistently to the two rear tires evenly by being mounted dead center on the axle and close to the vehicles center of gravity. Unlike most 3 link, 4 link, 5 link and leaf spring rear suspension systems, a properly designed TorqueArm system produces more total and more consistent weight transfer to the center of the rear axle during acceleration and braking due to a non pivoting consistent load point on the chassis that is constant in relation to the vehicle center of gravity of the sprung mass of the vehicle. This results in a car that is easy to control at the limits of adhesion on wet or dry surfaces, and while cresting hills while turning, minimizing steering corrections required of the driver.

65-70 Applications. Leaf springs are heavy and prone to wheel hop, and a geometric compromise as they have to carry all acceleration loads, both longitudinal and lateral, and deliver engine and brake torque to the rear tires. In a performance application wheel hop is usually controlled by the addition of control arms and adding leafs to the springs. Though and improvement, this is a compromise at best, and in a high performance cornering situations vehicle behavior is still not ideal. Addition of a TorqueArm removes the engine and brake torque from the springs, and delivers it evenly to both rear tires, and consistently relative to the vehicles center of gravity. Further, installing a Torquearm with a Watts link or Panhard bar, along with Ball pivot lower control arms, and either floating the springs on the axle with sliders or replacing them with coil overs provides a uniquely superior driving experience and perfects the rear portion of a formerly leaf spring suspended vehicle.

79-04 Applications. As delivered, the major limit in handling and overall performance of 79-04 Mustangs, and similar cars with like chassis design is the 4 link rear suspension geometry. With the upper two control arms angled heavily outward to laterally locate the axle, the lower and upper rear control arms are not parallel, so as the suspension moves the upper arms are twisted in their bushings. During performance driving this quickly leads to a near total binding of the rear suspension, called “roll-bind.” The binding action as the body rolls acts like a hugely progressive rear anti-roll bar, causing the rear roll stiffness to skyrocket at some point in the corner, and the sudden change in tire loading across the rear tires induces sudden oversteer. Further the layout locates the rear roll center far too high and migrates up and down substantially with small changes in ride heigh, which causes other detrimental handling effects.

The TorqueArm along with a Panhard bar or Watts Link and lower control arms with a ball mount in at least one end is the best solution to completely eliminate roll bind, properly locate the roll center, and provide constant engine and brake torque loading of the tires relative to the CG. This results in a confidence inspiring and very enjoyable high speed driving experience in a high powered car without the need of electronic driver aids.

05-14 Applications.  The 2005-2014 or S197 chassis withe its 3 link and Panhard bar design is a great improvement over earlier years, as roll bind has been all but eliminated and the roll center is better located and more consistent relative to the center of gravity. However the single upper link yields broad changes in load relative to changes ride height due to its short length. This results in undesirable changes in tire loading as ride heights change which can contribute to wheel hop and less stable and consistent cornering behavior. Removal of the short upper link and installation of a TorqueArm, and along with Lower control arms with a spherical bearing in at least one end of the arms improves the high performance driving experience considerably and is the best solution to the =wheel hop issue inherent in these cars.

Other Applications. Beyond the above applications, we custom design and manufacture TorqueArms for 8.8 and 9 inch rear axles into any car for most any application.  If you have any specific questions regarding your particular application please contact us at (707) 939-2244, or email

** See Life time warranty

For more information about how a Torquearm fits into a complete performance system Please review the following:
“Been There, Done It All” October 2004, 5.0 Mustang and Super Fords
“Extreme Winner” May 2005, 5.0 Mustang and Super Fords
What Are You Going To Do With Your Car
The GR40 Suspension System
“Vortech Mustang Mach 1” April 2004, Motor Trend