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Street Race Truck More... The Toolbox

Upgrading Rear Control Arms on an A-Body


Speedway Motors employee Steve is back at it with his Laguna build. This time Steve tackles the rear control arms, upgrading the factory stamped set with a more rigid boxed set from Speedway Motors.

One of the inherent problems in getting the power to the ground in a GM coil spring rear suspension is dealing with the weak stamped steel rear control arms. They are a great choice for your everyday 9-5 daily driver, but the minute you start adding more horsepower to the mix, the stock rear control arms are done. The channel style just can't handle the increased power without starting to flex, and that's no good.

Speedway Motors has an easy and inexpensive solution to this problem with their 1973-1977 GM A-Body Rear Control Arms. They're available in two options, the first option is P/N 916-34053, it's a complete kit with the upper and lower control arms, and all the bushings included. The second option is P/N 916-34051, it's just the upper and lower control arms only, and doesn’t include any bushings, allowing you the option to use any style of bushing you choose. I chose option two, because I wanted to install a set of Spherical Control Arm Bushings from Speedway Motors, P/N 916-34048, to allow the rear suspension to move more freely.

The Rear Control Arm Kit comes with the 916-34050 lower control arms, and the 916-34054 upper control arms. These are available separately in the event that you would need to replace them due to an accident or some reason.

As you can see there's a vast difference between the flimsy stock rear control arms and the stout boxed Speedway Motors rear control arms. The upper control arms are made from .083 (14 gauge) wall square tube with 1/4” thick brackets, and the lower control arms are made from 1-1/2” x 2” x .083 (14 gauge) wall rectangular tubing making these a very strong set of control arms. The lower control arms do not have provisions for mounting a factory stock rear sway bar, but not to worry, if you need a rear sway bar, they are available from aftermarket sources.

The original factory control arms are made out of stamped steel and just don't have the strength that comes from ones made from thick wall steel tubing. These will make a world of difference in the handling of your Gen 3 GM A-Body.

You can see the difference between the aftermarket and OEM control arms.

The installation can be done easily in a matter of about 2 hours in your driveway without any special tools needed. The tools that are required are:

  • 3/4” Deep and Shallow Sockets 1/2” Drive
  • 11/16” or 5/8” Shallow Socket 1/2” Drive
  • (depending on the size of the rear shock lower mounting nut)
  • 1/2” Drive Extension
  • (approximately 8”-10” long)
  • 1/2” Drive Breaker Bar
  • 1/2” Drive Ratchet
  • Hammer
  • Pry Bar (you can even use a jack handle if you don't have a Pry Bar)
  • Punch or an Old Phillips Screwdriver(for tapping the bolts out of the arms)
  • Floor Jack and Jack Stands (for raising and supporting the car safely)

To begin, find a flat, level, hard surface to work on, and block the front wheels securely. Jack the rear of the car up as high as needed and place jack stands under the frame rails behind the rear axle centerline. After lowering the car down on the jack stands, make sure the car is stable and doesn't move before getting underneath it. You'll want to keep the floor jack under the center differential to support the rear end housing while you swap the rear control arms (it makes it easier to reinstall the bolts, I learned this after doing one side). It doesn't matter whether you start with the uppers or lowers. The lower shock nut will need to be removed and the shock moved to the side to remove the front bolt on the upper control arm.

The task of replacing the rear control arms is a relative easy task and can be done easily by anyone right in thier own driveway, or in my case - the small garage at my apartment.

The upper control arms fit very nicely and look great, even though no one will probably ever see them; you'll know how great they look.

The lower control arms were by far the easiest to install, it took just a matter of a few minutes per side, and the increase in strength over the stock ones will be awesome. This is a very easy and necessary upgrade to you GM A-Body Car, and you'll feel the difference on the road as well as see it on your timeslip at the track. Do your car and yourself a favor and get a set of these installed. While you'll thank yourself for doing it, your competition at the track will hate you for it.

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