The golden rule of an overland vehicle can be summed up as “stock is better,” but things do not always go as planned. This would hold true for the ease of sourcing parts especially internationally. We take dive into looking at how to create a stronger drivetrain and moving away from the factory independent front suspension.
Five-What? Behind The Build
A sinister-looking Colorado in its natural habitat.
When people hear “five-cylinders,” they tend to go cross-eyed, and their heads cock to one side. The first generation Chevrolet Colorado features an Atlas inline five-cylinder motor. It was used to maintain a balance between the EPA standards and adequate power for the drivers’ needs. Invariably, overlanding probably didn’t make the shortlist of the designers’ intentions.
Just a few years ago the 3.5-liter gave out and we transplanted a newer five-cylinder with a bigger 3.7-liter displacement. Little did we know placing the motor into the truck would be the easy part. As it turns out, GM cleverly changed a few internals between the 2007 and 2008 model year. We found that by adding a sensor port and changing one of the cam reluctors, we only needed to employ the previous motor’s fuel system and wiring harness to complete the transplant.
Left: before and after porting and polishing along; right: the bent valves that caused the whole mess.
An issue arose when we found two bent valves, which spoke to the hastiness of our seller and the “great” deal. While the head was off, we took to the bench and gasket-matched the exhaust ports and smoothed out the intake runners, making this one of the few ported and polished Atlas motors in the world. Shortly thereafter, a tune and some fluids were all that were needed to get the engine running properly.
The intake system was custom-built from electrical conduit with one continuous bend. It had the same ID throughout its length to help keep air flow at its maximum. While the off-the-shelf varieties from K&N and others were proven and CARB-legal this setup showed that with a few tools and a little knowledge, we could create a functioning intake for a fraction of the price.
The custom intake flows better than the bolt-on variety and along with the Supersparkz helps the motor run more effecient.
The throttle body ported and polished by Supermodulation. They also hooked us up with SuperSparkz which are made from beryllium copper alloy rods that replace the springs between the coil packs and the spark plug. These offer a faster and hotter spark, improving throttle response and smoothing the idle.
On the exhaust side, we have a stainless header that is a drop-in replacement for the factory manifold that has a terrible reputation for cracking and breaking in multiple pieces. The stock midpipe that houses the primary catalytic converter has been flattened to clear the torsion bars that once resided in that area. The crushed sections have been replaced with a straight piece of pipe. Two Imco chambered mufflers rounded out the sheer rasp and gave this truck a manageable rumble.
8 switches running all our lighting needs. Out of the way and within reach.
What is a good overland vehicle if the cabin isn’t comfy and quiet? Whether we’re driving down to the parts store or bouncing down the Rubicon we need to make sure the cabin of the truck is comfortable. Even though the truck is a four-door and GM led their ad campaign with three grown adults in the back seat this is not the average payload the truck will see.
Space is at a premium and everything needs to be accessible and functional, but not without the creature comforts. Two JL Shallow subs reside under that back seat along with an Alpine amplifier. An overhead console from an early 2000s Trailblazer keeps the switches and small items up and out of the way. Currently, there is a seven-inch touch screen head unit in the dash, but plan to install and test out an Android-based head unit soon.
Our supervisor, making sure the 12-bolt is being installed correctly.
From IFS To Solid Axle
This truck is on its fourth rear axle and despite its lack of four-wheel-drive, we didn’t let that deter us from making this into a trail capable rig that won’t leave us stranded. Several years ago, while many miles up the trail, we broke an axleshaft on the stock AAM800 axle.
Being a C-clip axle, it didn’t take long to realize this was a major issue. A week later, the truck received a GM 12-bolt which had already been geared to 4.88:1 and had an Eaton Posi-traction locker. Maintaining the Chevy six-lug bolt pattern was an added convenience. Currently, a C-clip eliminator kit is on order to accompany future plans to convert to disc brakes.
The AAM 800 didn’t take too kindly to coming to a dead stop at 30 mph.
The solid axle up front started out as a simple concept – leaf springs and an ‘off the shelf’ hanger kit for a Toyota or full-size Chevy. As time went on, a linked suspension seemed to be more attractive given the strength and comparable cost.
However, no kits were readily available for what we needed; a modified three-link was settled upon. The side with the carrier would employ a radius arm and the other link would be a single bar. This gave the Colorado the most articulation with the best driveline angles.
From dream to reality, the front axle came from nothing to flexing.
After purchasing all the coil buckets, brackets, and heims from Barnes 4WD along with a passenger drop low-pinion Dana 44, we thought we were ready to install. Hours of research with countless pro and con lists later, we set off to locally source a Ford high-pinion, driver drop Dana 44. By swapping the Chevy outer shafts, flat top knuckles, spindles, and hubs, we now had a six lug, driver drop, Ford high-pinion front axle assembly.
A first-gen Nissan Xterra steering box with a rotated stock pitman arm all tucked into its new home.
Nonetheless, a Frankensteined axle is useless without the proper steering box. We would need to run a stout steering box with the goal of running 37-inch tires. Nissan had a great idea when they used a Delphi box under their first-generation Xterra’s. An outside frame mount, four mounting bolts, a huge sector shaft, and metric fittings all made this a perfect candidate for our build. Still, setting all the components on the driver side frame rail was tricky with the steering box, track bar, and coil bucket.
Setting the ride height are a set of Deaver coils meant for a full-size Bronco. While the weight of a Colorado is different, we felt that the softer spring rate of the Deaver coils and the addition of a bumper and receiver up front would even out the ride quality. The ride now is actually comparable to the ride the truck had previously.
Shocks were sourced through Summit Racing who have a distribution center in Reno which made it really easy to get the parts we needed quickly. Pro Comp ES9000s fit the bill. We installed 14-inch shocks up front and 12-inch shocks in the rear. We estimate this truck will now score nearly 800 points on the RTI (Ramp Travel Index).
Building The Rest Of The Truck
The idea arose to create a rack for over the bed, not to make it look like a lumber rack like you see on some construction vehicles, but more like a chase rack. The design evolved and we ended coming up with what we call a slant back rack. Two straight sections the same length bent in the middle so the rack would have a little bit of a rake to it on the top. A massive street sign sufficed for the top and we added some load bars from a mid-90s Suburban to the roof and rack.
The slant back rack over the bed not only looks cool, but it is also aerodynamic (as much as a lifted truck on 37s can be).
More tube work up front was made out of 1.75-inch DOM tube and was made to fit snug against the headlights and grille while still offering protection from a front impact. The front bumper also incorporates a two-inch receiver that ties the two frame rails together.
The skid plate is quarter-inch-thick aluminum, which is light and strong. Meanwhile, the rear fenders needed to be cut for two reasons: the wheelbase was stretched over three inches, and the rear axle needed to be moved rearward an inch due to the pinion length of the GM 12-bolt (it was a cheaper option than having the drive shaft shortened). Also, the departure angle is now drastically improved behind the tires, allowing minimal trail damage.
With the swap complete it is, even more, fun to hit the dirt in the truck.
The transmission is still a two-wheel-drive 4L60E and at the young age of 160k miles, it’s a good idea to rebuild it before we hang dual cases off the back. Ultimately, we will link and coil the rear suspension, finish the drivetrain, complete the tube-work, and add whatever else we can come up with.
Stay tuned for more of this build in the coming months.