Face it, if like-new or maybe even better-than-new performance is what you want from your Mopar's suspension, it will likely need a comprehensive rebuild. Under normal use, the stock Mopar front suspension lasts about 100,000 miles. The fact is, even with fewer miles under hard use or over a long period of time, things can get mushy; and, unfortunately, the required chassis lube-job has become an almost-forgotten routine.
The Mopar torsion-bar suspension was perhaps the finest front-suspension design of the period because of Chrysler's innovative and efficient torsion-bar springing and unequal-length control arms. The system featured torsion bars hex-anchored to a ridged mid-chassis-mounted crossmember and keyed to the lower control arm by an adjustable mounting socket. In turn the lower control arm is secured to the solid K-member via a rubber-bushed pivot shaft. The lower control arm is triangulated to the K-member by a forward-facing strut rod that forms the second leg of the lower A-arm. The strut rod solidly transfers the fore and aft forces of the front suspension during braking, acceleration, and cornering. The upper A-arm is formed like a conventional wishbone, pivoting on two inner bushings. The spindle mounts between the upper and lower control arms via two large spherical ball joints.
This '70 Swinger 340, now...
This '70 Swinger 340, now a rolling chassis, will get a better-than-new front suspension.
Most trouble begins with the ball joints. It's internally supported by low-friction nylon inserts that require routine lubrication. After the factory lube, the grease fittings were snapped, requiring the fitting of new zerks for service lubrication. All too often the service lube never happened, resulting in worn-out ball joints. The same situation occurs with many ball-jointed tie-rod ends.
Next we have the bushings. The most critical bushing in the system is in the lower control arm. The pivot shaft is rigidly mounted to the K-member, and the torsion-bar socket at the other end pivots with the lower control arm. This disparity in motion is wholly absorbed through the twisting rubber in the lower control-arm's pivot-shaft bushing. Eventually the twisting takes its toll and the bushing fails. Then we have the strut rod, rigidly mounted to the lower control arm but bushed at the forward K-member mount to allow for articulation through the suspension's motion. The forces on the strut bushings are primarily fore and aft, and whenworn, they cause the lower control arm to shift forward and back at the ball-joint end, making the suspension unstable. Up top, the rubber upper control-arm bushings are subject to normal wear, and they too eventually blow out.
Bed rest doesn't do the suspension any good; the only cure is a rebuild. The best approach is to blow it all apart and replace everything, using an aftermarket rebuild kit. This '70 Dart Swinger 340 is in the process of a full rebuild, and a fresh front suspension is on the list. While rebuilding the front suspension piecemeal on the car is the norm for service, in a resto, pull the entire works from the chassis in one hit. The bulk of the suspension and steering system is mounted to the K-member, allowing removal as a unit by dropping the "K."
Though rebuilding the suspension in the car while lying on the cold concrete can be some seriously dirty penance, with the K-member out the job is nothing short of enjoyable. A number of tricks we've developed over the years make the job easier. This month, we'll cover the removal of the complete K-member and front suspension from the car, and weld-up a rig that allows us to mount the K-member to an engine stand for service. We'll show what it takes to break it all down and pass on the hard-learned tricks of the game.
The key player up front is...
The key player up front is the K-member, bolted to the front chassis rails by four large bolts; it carries the engine, steering, and front suspension systems. The engine is already clear. Dropping the K-member now will relieve the body of its front suspension and steering.
With the chassis up high on...
With the chassis up high on heavy duty jackstands for clearance, unload the front torsion bars. Just unwind the adjusters at the lower control arm.
Everything that links the...
Everything that links the body to the "K" has to be unhooked, including the shocks' upper mounts and the steering-column connection at the box..
Removing the torsion bars...
Removing the torsion bars is usually the toughest part of the job, but here's an easy way: Remove the rear retaining clip as usual from the rear anchor, and then take the nut off the pivot shaft where it goes through the K-member (A). Next take the front nut and bushing off the strut rod (B) where it goes through the "K." Now the entire lower control arm can be levered back, which will push the torsion bar out of the rear anchor. The bar can usually be pulled out of the lower control-arm socket by hand. If it's stuck, separate it with a few hammer taps on the torsion-bar socket of the lower control arm.
Disconnect the upper A-arms...
Disconnect the upper A-arms from the body by removing the pivot/adjuster bolts. Lever the arms up and out with a crowbar or large screwdriver. On swaybar-equipped cars, the bar prevents the suspension from swinging too far down. On non-swaybar cars, wire the lower control arm to the "K." Don't forget the brake-hose connection to the body.
With everything free, support...
With everything free, support the K-member with a jack (make sure it's secure, preferably strapped), and unwind the four bolts that attach the "K" to the rails. It's a heavy unit, so keep clear from underneath while unbolting.
With the frame in place, the...
With the frame in place, the suspension assembly bolts to the stand for easy access and a comfortable working height. The heavy hooks linking the strut rods to the frame keep the suspension from drooping.
Lowered, off, and out, it's...
Lowered, off, and out, it's time for a tear-down and rebuild. The strut rods are wired to the K-member to keep the suspension up, preventing the brakes from dragging on the floor.
Mopar Muscle's Steve Dulcich...
Mopar Muscle's Steve Dulcich invented and fabricated this frame that allows us to mount the K-member to the engine stand. The angle iron "outriggers" bolt to the four K-member mounting points, and the tall, flat steel plate at the back mounts to the engine stand.