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Part 3: Sure Footed FlyerThe Interceptor Gets a New Front End From the May, 2004 issue of Mopar Muscle By Marko Radielovic Photography by Marko Radielovic
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Having been straight-line guys for most of our car lives, building an open-road racer is a foray into the unknown. The front suspension on our '89 Diplomat cop car was shot and in need of a freshening up. A clean bill of health, issued before we begin the modifications, will enable this portly beast to handle well and remain stable at speed. Our goal to run the Nevada Open Road Challenge in May is quickly approaching, and a good tight suspension is paramount to our quest for speed. The Diplomat has a very unique suspension. Unlike those we are accustomed to in our traditional A-, B-, and E-Body musclecars, our Dippy features a transverse torsion bar front end that is rather unique and a bit confusing for the uninitiated. Introduced in 1976 on the new Dodge Aspen and Plymouth Volare F-Bodies, the transverse torsion bar was also the suspension of choice for the M-Bodies, such as the Grand Fury and Diplomat. We contacted Just Suspensions for one of their complete front-end kits, and then contacted Koni for a set of shock absorbers. We dragged all the parts to Sleeper Suspension Development in La Verne, Califorinia, rolled up our sleeves, and dove in. The decision to use Sleeper's facilities to help with this project was made because of Jim Sleeper's vast experience building a variety of race cars for numerous types of racing. Later we'll add trick new Quickor sway bars, and incorporate a couple of other mods to help our Diplomat along on its quest for high-speed stability.  (above & below) Our Diplomat...  (above & below) Our Diplomat came equipped with a transverse torsion bar suspension.Ours looked a bit worse for the wear and was a bit sloppy especially atspeed, inducing a high pucker factor. We intend to cure our pursuitvehicle of this unwanted ill behavior.  Just Suspensions provided...  Just Suspensions provided us with this complete rebuild kit thatincluded upper and lower ball joints, upper and lower control armbushings, an idler arm, a pitman arm, tie-rod ends, upper and lower bumpstops, sway bar bushings, plus (not shown) all of the dust covers andhardware.  Jim Sleeper of Sleeper Suspension...  Jim Sleeper of Sleeper Suspension Development spec'd out the Koni shockabsorbers (PN 80-2660 front, PN 82-1255 rear) we ordered for ourhigh-speed cruiser. Our shock mounts would need modifying to use thesepieces, as Koni doesn't offer an off-the-shelf, high-performance shockfor this rather odd application. Not many people are buildingopen-road-race, late-'80s police cars for some unknown reason.  After we removed our front...  After we removed our front tires, we unbolted the tie rods, hung thebrake calipers out of the way (removing them would later require a brakebleeding), unbolted the torsion bars, and backed the adjusters all theway off to remove tension. Now disassembly is possible.  (above & right) When we unbolted...  (above & right) When we unbolted the bottom of the shock absorber, extraction of theshock necessitated the removal of the lower control arm, as the shockcan't pass through the top. Before the control arms can be removed, theball joints need to be separated, and the torsion bar and sway bar mustbe disconnected. Remember to separate the sway bar on both sides, asundoing only one end will cause it.  While attempting to remove...  While attempting to remove the lower control arm on the passenger sideof the vehicle, we discovered the nut on the bolt holding it in placewas tack welded to the bolt. This discovery prompted us to check thedriver side, where we found the same scenario. Was this a normalpractice by the factory on police cars? Removal of the nuts damaged thebolts, forcing us to replace them.  Prior to unbolting the upper...  Prior to unbolting the upper control arms, we removed the upper balljoints. The uppers in this case are of the screw-in variety, requiring aball joint socket and an impact wrench. The bottom ball joint would haveto stay in place until we removed the lower control arm, as they are ofthe press-in variety.  The steering link requires...  The steering link requires a puller to properly separate it, limitingthe possibility of damaging the pieces.  Our lower control arms required...  Our lower control arms required modifications to the shock mount, as ournew Koni shocks employ an eyelet in place of a bolt-through stud.  (above & right) We made the...  (above & right) We made the necessary cut to clear the bottom of the shock and drilledthrough the side of the lower control arm for a grade-8 bolt. In thenext installement, we will box the lower control arms for strength.  With both the upper and lower...  With both the upper and lower control arms removed, we went on adegreasing binge. This is your only opportunity to strip these parts andpaint them, so take your time. When the paint is dry, you can move on topressing in the various bushings, bump stops, and lower ball joints. Ashop press proved invaluable. Jim Sleeper then set the toe,... Jim Sleeper then set the toe, caster, and camber. Torsion Tension and Ride Height
Us Mopar guys and gals have always held our torsion bar suspensions near and dear to our hearts. Why? Well, for one, we have the option of raising or lowering our ride height to suit our needs or desires with the turn of a 3/4-inch wrench. The same holds true for transverse torsion bar suspensions systems. That built-in adjustability comes at a price, though, as the raising and lowering of the front end affects suspension pre-load. The torsion bar is simply an oddly-shaped coil spring with a given "spring rate". Lowering the suspension takes pre-load away, causing the suspension to react at a slower rate of speed, while the opposite holds true when the torsion bars are cranked up and the front end is raised. We opted for a lower ride height in order to punch a smaller hole through the air with our vending-machine-like aerodynamics. It's a compromise, but one we were willing to make in the pursuit of top-end stability.  Our good friend Casey Steinman...  Our good friend Casey Steinman continued to march--despite an attempt tobreak his hand with a sledgehammer by yours truly. Casey is seen herescrewing in a new upper ball joint.  Reassembly is pretty straight...  Reassembly is pretty straight forward, and not nearly as messy now thatour parts are refurbished.  With the front end back together,...  With the front end back together, we made our way to the rear of the carto bring it up to speed--so to speak.  Since an altitude adjustment...  Since an altitude adjustment was in order to lower the Diplomat's centerof gravity, we employed a set of universal lowering blocks from ourlocal parts emporium. The 2-inch blocks moved the rear axle closer tothe body, requiring shorter sway bar links.  As a consequence of lowering,...  As a consequence of lowering, the shock mounts needed modifying to lowerthe bottom mounting point in order to increase the shock absorber'stravel. Had we not, we would have been compressing the shock and,thereby, shortening its travel and effectiveness. Also, the factorybottom shock mount employed a bolt-through stud system, necessitatingone that would accept an eyelet. Rod ends with grade-8 bolts were chosento mount the shocks.  A shorter sway link was located...  A shorter sway link was located to address the 2-inch relocation of theaxle. The 2-inch lowering blocks were of the universal variety, meaningthey were no good for any specific application in stock form. Somemassaging was required.  (above & right) These before...  (above & right) These before and after shots show the 4x4-like stance of the Diplomatbefore we lowered its center of gravity and the end result.
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