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The 1978-1987 GM G-Body: Inexpensive, plentiful, lots of room under the hood, making it a great platform for a drag race project. The 1964-72 12-bolt A-Body rearend: bulletproof, with an enormous range of aftermarket gearsets, axles, lockers, and LSD’s. Together, they’re a combination that’s hard to beat, and Spohn is making that swap a little easier with their new upper control arms to mate the 12-bolt to a G-Body. You can get them with poly bushings for streetable applications or hardcore Del-Sphere pivots for full time track duty, these arms are double-adjustable for pinion angle changes without unbolting the suspension, and they’re available in a range of powder-coat colors.
Official Press Release:
Our tubular rear upper control arms outperform the flexible, stamped-steel arms and soft rubber bushings that come from the factory. Eliminate wheelhop and increase traction with an easy bolt on installation. Adjustability feature allows for setting the pinion angle. Our right hand and left hand threaded CNC machined male/female double adjuster allows for easy on-car adjustments, no need to unmount the control arm to make adjustments!
The control arm bushings on G-Body vehicles have a significant impact on your vehicle’s ride, comfort, handling, acceleration, noise and vibration. When the vehicle leans (rolls) in a turn, one side of the chassis moves up relative to the rear axle and the other side moves down. The control arms must twist to allow for the axle to articulate, this causes the control arm bushings to bind. If this bind becomes excessive, it will raise the rear wheel rate and produce sudden and uncontrolled changes in handling such as snap oversteer.
The factory minimizes this suspension bind by using compliant rubber bushings. These soft bushings help accommodate the necessary motion of the control arms during body roll. However, the rubber bushings do not provide much in the way of forward and aft support which can cause wheel hop during hard acceleration and braking.
It is common to replace the stock rubber control arm bushings with polyurethane bushings to resolve the shortcomings of the factory’s soft rubber bushings. Polyurethane bushings eliminate wheel hop, reduce axle deflection, and improve straight line traction. However, the downside of polyurethane bushings is they prevent the necessary movement of the control arms during body roll, which in turn produces significant binding in the suspension when the vehicle is cornering. The polyurethane bushings also place high stresses on the control arm mounts on the vehicle. Polyurethane bushed control arms do not allow for rotation of the control arm during cornering because of the stiffness of the bushings.
Build Specifications:
- 3/4″ Del-Sphere Pivot Joints
- Right hand and left hand threaded CNC machined and silver zinc plated 4140 chrome moly double adjuster threads into 4130N chrome moly TIG welded threaded tube adapters
- Ship to you jig set at OEM length
- Extended length CNC laser cut and formed 1/4″ steel mounting brackets fit all OEM and aftermarket rear ends
- Re-uses OEM mounting hardware, no need to drill out your car’s mounting bracket holes.
- These are the highest quality, easiest to adjust on the car rear upper control arms on the market!
- Available powder coated in your choice of the above colors.
4130N Upgrade: The ultimate in bullet-proof lightweight strength, 100% TIG welded chrome moly construction! Same as above, but constructed entirely from 4130N chrome moly tubing.
