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Burning up the telephone lines for weeks at a time to vendors like Dynatrac, King Shocks, Bilstein, Tom Woods and many others was all part of the deal, and was time consuming to say the least. The key to building any vehicle is homework, homework, homework. The truck was built mathematically and dimensionally on paper before the first dollar was spent. The first part fabricated was the four link center support mount, using ½ flat plate. 9/16 I.D. holes were punched into the backbone of the mount. After checking square, the entire piece was welded out. The backbone-to-roof and roof-to- edge welds were smoothed, to show winning standards.
Before the rear 4-link control arms could be fabricated, the rear axle needed a fairly complex set of mounts and brackets for the arms, coil-overs and shocks. The AAM 11.5 rear axle was a good stout unit that came with the truck, so it was re-geared with 5.13:1 gears, Timken bearings and National seals wrapped around an AAM posi-traction differential.
All of the control arm mounts, shock mounts and coil-over mounts were fabricated from ½ steel plate.
This is a look at the rear upper coil-over mount hoops and the twin upper shock mounts. Fabricated with 2.0X .120 DOM tube and ½ plate for the hoops, and the shock mounts were formed from 1.25X .500 DOM tubing with .250 thick gussets.
In order for the rear upper coil over hoops to be braced properly, but still allow use of the bed for carrying dirt bikes and four wheelers(!) we decided to anchor the support brace to the top of the frame rail. This required slightly tubbing the rear fender wells by 4.0
After mounting the backbone center mount, work began on the rear control arms, using 2.0X .500 wall DOM for the arms, and 2.0X.225 for the bushing ends.
Here the adjustable upper control arm mounts are being fabricated, again from ½ Steel plate, with ½ steel gussets. The boxes were attached to the frame itself and heavily gusseted.
Again, you see the ½ plate control arm mounts, along with the 2.0X .500 wall DOM Tube control arms, fully polished welds and jam nuts to lock in the required adjustment.
In order to make room for the rear 4-link control arms, the factory fuel tank needed to be relocated. We found a similar capacity steel unit designed to fit between the rear frame rails, instead of the factorys inside frame, north-south style. The original fuel pick-up/sending unit was then grafted into the steel tank so computer functions such as mpg, miles to empty and the Duramax % of oil life until change needed, would all work properly. The fuel cooler was also relocated closer to the new tank, using steel line and high pressure hose compatible for the diesel fuel. A new rear cross-member was fabricated behind the fuel tank to offer extra impact protection.
After polishing all the welds and setting the pinion angle, the Kings and Bilsteins were bolted up and clearances checked.
EGL freight brought us our new Dynatrac front Pro Rock 60.
We had elected from the start to use a Dynatrac product, due to the pleasant experiences we have had with them in the past, plus they offer really useable options for extreme applications such as this truck. The Dynatrac H.D. knuckles and F-550 brakes capped off the ARB air locker, the 5.13 gears and the 35 spline inner and outer chromoly axles.
After using a trio of lasers to center and locate the axle side to side and front to rear, The upper and lower control arms were fabricated, again out of ½plate. The lower mounts are identical to the rear axle lowers, but the uppers took on a life of their own.
Jamie is forming the radius mount that goes inside the front upper coil mount see on the right, in mock up. also notice the upper control arms in their unfinished state, compared to the shots of the rear arms that had been smoothed earlier in this article.
The Dynatrac steering arm that was purchased with the front axle was not going to work for this application due to the wheel travel the truck was designed to have. The tie rod ends would encounter bind during high mis-alignment conditions, so we used a slighty longer drop pitman arm on the steering box, and sat down at the computer and fired up Solidworks. After drawing the new steering arm in 3d, we made a template for trial fitting. Things looked good, so we copied the draft onto CD and fired it off to the machine shop to be carved out of an 8X 8X 12 chunk of billet steel.
After installing the new steering arm, a drag link was built out of 1.25X .250 DOM using 1 ton 7/8 tie rod ends. We chose not to use rod ends due to the normal wear the truck would be seeing, and the noisy rattles that accompany the wear. The original steering box and steering pump was sent to West Texas Off-Road in San Angelo to be ported and tapped for external lines and the pump performance to be enhanced to carry the extra load of a hydraulic assist ram. The ram would assist the steering box in turning the big (heavy) 49 IROK Super Swampers while also removing physical stress loads from the box and frame.
All of the 4-link trucks we had seen in the past, with a couple of exceptions, had extremely poor drivability due to various reasons. Some had geometry issues (or lack thereof) some had scary steering issues and some were using a combination of leaf springs with shackles on each end of the spring with a hap-hazard 4-link to keep it somewhat under the truck. But all the trucks seemed to have one major problem in common: body sway or lean. We called up a small mom and pop shop, which makes their living selling sway bars to Nextel Cup teams and ordered a set of gun-drilled and splined bars specifically rated for our application for the front and rear of the truck. Since the NASCAR boys are sneaky and secretive, the bars do not have any type of standard mounting system, which required us to build our own. Using a 1.0 thick chunk of T-6 aluminum, we machined 4 sets of main caps that held in bushings we machined out of UVRA urethane round stock.
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