The idea for changing the rear suspension on a muscle Mopar came to mind while walking the Manufacturers' Midway at the '07 Mopar Nationals. There we noticed a triangulated four-link rear suspension system-originally designed to fit an A-Body Mopar-at RMS Suspension's booth that really caught our eye. After talking to RMS Suspension's Bill Reilly about the system, we decided we needed to take a closer look at this cool setup.
We came back from the Mopar Nationals very excited about the idea of doing something cool and different. We were also curious to see how well the A-Body system would fit.
Here is the fully assembled...
Here is the fully assembled factory style rear suspension with SS springs and MP 50-50 four-speed drag shocks. While it works at the track and on the street, there is something better.
The problem we did encounter at the time of planning was that there was no system offered for the B-Body we planned to work on. In our discussion with Bill, he agreed to send us an entire A-Body system to see if we could make it work in our '67 B-Body-with minimal altering of the components.
After Bill sent the A-Body kit, we dug into it to see if it would actually work on our '67 B-Body in its unaltered form. Surprise, no go. We contacted Bill and showed him pictures of how it wasn't going to work. At this point, he thanked us and told us to keep the hardware for our time and effort put forth.
Now, since we had some hardware to play with, we were destined to design our own triangulated system for this B-Body. We started off by finding exactly where we wanted the rear axle to be located in the car. We chose a location that set the rear axle back about 3/4 inch and slightly higher in order to lower the car. We did this to make room for taller tires and to give the car a more aggressive stance. Now with the rear axle in the desired ride height position, we used the adjustable lower bars from Bill's kit and made adjustable brackets that attached the lower link bar to the body of the car where the original leaf-spring hangers would have mounted.
To get started, we removed...
To get started, we removed the rear wheels. This isn't your typical restored Mopar, and we'll be able to test the link system thoroughly.
The next step was to create a structure that would attach to the framerails. We wanted this structure to be strong, and we also wanted to be able to mount everything to it except the lower four-link bars, which would mount to the chassis and to the axle. So with the help of coworker, Ron Linton, we came up with the required brackets and mounting points needed.
We started by cutting out the car's original crossmember. With that gone and everything ground smooth, we now had the desired space needed to make the structure. We wanted the structure to have secure mounting locations where it would attach to the framerails of the car. There are actually two crossmembers in this structure: a front and a rear. These two crossmembers are connected by two chrome-moly bars that are welded between them. This new boxed structure with two crossmembers is what gives us the four mounting points. This is necessary for high-horsepower applications. Since the upper link bars attach to the chassis of the car at the structure, a great torsional twist is applied to it due to the force from pinion rise during launch and under acceleration through those upper four-link bars. Because of this torsional force, it was necessary to spread that energy over a greater area of the chassis-the reason for the four mounting points.
It doesn't matter whether...
It doesn't matter whether your Mopar is using drum or rear disc brakes, they gotta come off.
Luckily, Irons' shop is equipped...
Luckily, Irons' shop is equipped with a lift, so we have more room to work. Since a kit is now available, you can do this with the car on jackstands, but a lift makes it easier.
With the axle supported and...
With the axle supported and hanging in a relaxed position, we removed the rear springs and then the axle from the car.
At this point, the rear shock...
At this point, the rear shock plates and shocks can be removed.
Designing the structure this way also allows us to use the rear crossmember to mount the rear coilovers to the chassis. This is a very strong point for the weight of the car to be supported. We now have a one-piece weld-in structure that the suspension mounts to. The beauty of this system is there is minimal altering to the car. The factory sheetmetal crossmember needs to be cut out, a little paint needs to be ground off for welding, and the four mounting points need to be welded on the inside of the framerails-that is the extent of the alterations to the car.
We wanted the car to work well on the dragstrip and have great road manners, and it does. The car seems to be smooth under launching and acceleration. There is no snap or wind up of the suspension during launch. It has a firm positive feel on the road. In addition to the many benefits this system has over the stock leaf-spring suspension, the entire system is also 50 pounds lighter than the stock-style suspension using super-stock leaf springs.
Now that everything is disassembled,...
Now that everything is disassembled, the factory rear shock crossmember needs to be removed. It can be cut out with a cut-off wheel. After the rear shock crossmember is cut out, the framerails need to be ground smooth so there is room for the new crossmember to be cleanly installed.
This is what the new rear...
This is what the new rear suspension pieces look like. The kit includes many cool pieces, such as fully adjustable upper and lower four-link bars and really trick QA1 12-way adjustable shocks and coil springs.
Now that the framerails have...
Now that the framerails have been ground smooth, the new tubular rear crossmember needs to be located and welded in place.
The lower four-link bars are...
The lower four-link bars are now ready to be installed on the car. Before this can happen, they need to be assembled. There is a bracket included in the kit. This mounts in place of the factory front spring-hanger. This bracket provides the mounting point where the lower link-bars attach to the chassis of the car. Note: It is a good idea to adjust both of the lower four-link bars to exactly the same length before the bars and brackets are assembled. This will help ensure that the suspension will go together keeping the car square.
Both of the upper link bars...
Both of the upper link bars can now be attached to the crossmember. These should also be matched in length like the lowers were.
The rear axle needs to be...
The rear axle needs to be supported and carefully positioned underneath the car exactly where the ride height will be. At this point, the weld-on tabs can be attached to the upper link bars. The weld-on tab and upper link bar assembly can now be lowered down on the axle tube to locate where the tabs need to be located. After positioning the tabs and spot-welding them, we removed the rearend and finished welding the tabs to the housing. Note: To be safe, we recommend removing the center section and axles so you can clean the axle tubes after welding.
The brackets that attach the...
The brackets that attach the lower link bars to the axle now need to be assembled. The first step is to bolt the aluminum lower shock attachments onto the brackets.
Now the shocks can be bolted...
Now the shocks can be bolted to the crossmember, and the rear axle can be rolled back under the car for installation.
With the rear axle supported...
With the rear axle supported under the car, the upper four-link bars can be bolted to the rear axle.
The bracket assemblies can...
The bracket assemblies can now be held up to the axle and the U-bolts dropped in. You will probably need a third hand to hold this together while the nuts are put on and tightened.
The shocks can now be bolted...
The shocks can now be bolted to the axle. Now that the shocks are attached, the support holding the axle up can be removed. At this point, the brake lines and the driveshaft can be reinstalled.
Now it's time to attach the...
Now it's time to attach the bracket assemblies that attach the lower bars to the rear axle. This bracket assembly is bolted on the axle using three U-bolts per side. Because of the length of the bracket, a second spring perch is used to support the bracket. It is not necessary to weld this perch to the axle because the original perch is used to locate everything. You can, but the second perch is only for support.
Now that the system is installed,...
Now that the system is installed, there are a couple adjustments that may need to be made. Shortening or lengthening the lower four-link bars will alter the wheelbase of the car by moving the axle forward or back. If the car is out of square, one lower bar or the other may need to be adjusted to slightly alter the position of the axle in the car. The upper four-link bars can be shortened or lengthened. By doing this, it tips the axle up or down, making the pinion angle adjustable.
With everything back together,...
With everything back together, it's time to set the car on its tires and make sure everything is square. At this time, we took the car for a couple of slow trips up and down the driveway, just to see if it tracks straight. If not, adjust the bars until it does.
Once you're sure everything...
Once you're sure everything is square and tight, launch it.