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Technical > Installation Guide

January 2005 Issue

Project: Maya Hunter

Part 1 - Suspension: Fine-Tuning The Foundation For Our Jungle Explorer

Editor’s note: This is the first of several installments on converting a stock 2005 Toyota TRD Tacoma 4x4 into a truly functional off-roading vehicle to tackle the harsh trail conditions that it will encounter in the jungles of Guatemala. Toyota Motor Sales, USA generously donated this vehicle along with Yamaha International’s donation of a Rhino vehicle to help the Vanderbilt University archeologists further their studies of Maya ruins in support of science and education of ancient cultures. Many other aftermarket accessory manufacturers who will be featured in upcoming installments also contributed greatly to the success of this very worthwhile project.

Undertaking any vehicle-related project requires pre-planning if the long-range goal is to have the end result meet a specific purpose. Look at it like you would building a house; the nicest ones are built when there’s a vision of what it’ll look like and how it’ll function long before the first batch of wet concrete hits the forms.

So it is with “Maya Hunter,” our project Toyota Tacoma that is named after Hunahpu, a mythical Maya hero. The name suits its intended use.

This shortbed 2005 Double Cab 4x4 TRD version is being prepared for use by Vanderbilt University archaeologists hunting for clues that will lead to a better understanding of the ancient Mayan civilization. The Tacoma will be used every spring to take them deep in the jungles of Guatemala — and back out.

In short, this project vehicle is going to see real-world use — both on the streets around Nashville, Tennessee, and on the backroads. Jungle backroads (or un-roads as the case may be).

By the time you read this, the keys to the Maya Hunter — and the specially prepped Yamaha Rhino that is also part of this jungle exploration package — will be in the hands of Dr. Francisco Estrada-Belli, the professor in charge of the Holmul, Guatemala dig site.

But we are going to take you through the build-up process in case you too want to take a 2005 Toyota Tacoma 4x4 to a higher level of performance to pursue your own off-road adventures.

Suspension Basics

With that in mind, our long-range plan is to keep reliability and functionality at the forefront of whatever we do. That said, our first goal is to increase ground clearance without compromising ride quality or load carrying capability. Not an easy task with today’s independent front suspensions.

By the very design of IFS, one is limited in how much lift can be achieved without compromising the reliability of factory upper and lower ball joints, axle CV joints, and hitting the bump stops of the suspension.

While we would have loved to see four-inches of lift to accommodate 35-inch tires for running muddy jungle roads, the reality is 33s and two- to three-inches of suspension lift is all that can be used with the new Tacoma without replacing A-arms and other suspension and chassis components with expensive aftermarket parts.

Resigned to not having a really tall truck, we turned to Skyjacker Suspensions in West Monroe, Louisiana, for help in setting up the new Tacoma with a jungle-ready suspension. They assured us they had everything we needed to setup a solid foundation for this project vehicle.

On The Lift

We told them the truck’s intended use and that it would have an ARB bumper and Warn winch on the front that would add some 200 pounds to the front suspension, while carrying a lot of gear and supplies on the roof and in the bed.

Skyjacker techs quickly pulled a pair of their Platinum Series coil-over shocks from their massive parts inventory that they felt would fit the new truck. They also provided us with a set of three-inch-lift Toyota leaf spring packs and a matching set of Platinum Series shocks for the rear.

Skyjacker’s Platinum Series shocks and coil-overs are awesome looking, and the build specs are just as impressive as the looks.

The Platinum Series shocks have a massive 2.5” O.D. steel cylinder (nearly twice the diameter of the stock Bilsteins) honed to +/- .001”. It is engineered with a 1” high-carbon induction-hardened, micro-polished steel shaft and has a heat-treated stainless steel valving for high temperature and high-pressure operation.

The piston is made from a 7075 alloy and fitted with a high temperature Viton wiper seal. Each end has a 7075-aluminum alloy rod end fitted with Teflon lined stainless spherical bearings to further increase longevity in the off-road environs.

To ensure the consistency of all the Platinum Series Coils, only 5160H alloy material is used. A CNC machine winds the Softride® coil springs with precision and each coil is then dimensionally tested through a meticulous check system to ensure proper specifications accuracy. Each spring is preset to add memory and eliminate settling.

They are then load tested at 100% of the vehicle’s curb weight. A final height rate test is used to certify the consistency of the pound rate through the complete travel cycle.

Unfortunately, with all their state-of-the-art designing, they had nothing specifically fit the ’05 Tacoma. They left figuring out that part to us — and our friends at the 4WD Specialist, a four-wheel-drive repair shop located about a mile from Skyjacker’s facility. Welcome to the world of prototyping on a tight time schedule.

[Editor’s note: This project vehicle was literally built in two weeks so it could be presented to professor Estrada-Belli on November 3, 2004 at the Specialty Equipment Market Association (SEMA) Show.]

What we found out in short order is the ’05 Tacoma is all-new in design, so parts, including the suspension and drivetrain, from the earlier model wouldn’t fit the new model.

Over the next two days Josh Hodge, owner of 4WD Specialist, and Charles “Chucky” Robinson, one of his ace mechanics, nearly wore out their arms, air guns and wrenches installing, measuring, removing, adjusting and re-installing suspension parts.

The first set of coil-overs were both too short and too light on spring weight to give the Maya Hunter the 2.5-inch lift and ride we were looking for. We also encountered a problem with the larger size of the Platinum Series coil-over assembly; being nearly twice as fat in diameter as the stock Toyota/Bilstein unit, the upper mounting points didn’t match up and the bottom coil base interfered with both the axle shafts and the anti-sway bar that is now forward-facing.

In addition, the rear leaf spring packs on the new Tacoma have the spring-center bolts centered on the spring pack while the Skyjacker leaf springs for older Tacomas is offset a few inches toward the rear. No fit there, either.

So, back to Skyjacker. Because of the serious time constraints on finishing the truck, their answer to the rear spring problem was their Softride Add-A-Leaf kit to use with the stock leafs springs.

As for the front, they figured out that the new Tacoma, which is heavier than the earlier model, would be better if it was setup with Tundra front coil-overs, along with a 1-1/2-inch-tall machined aluminum spacer to keep the coil spring cup from coming in contact with the axle shaft.

New parts in-hand we went back to our hoist-bound Maya Hunter.

We moved the anti-sway bar mounts forward 3/4-inch on the frame to clear the larger coil-overs, installed the special spacer, adjusted the spring collar to a position we thought would be close to giving the proper ride height, and bolted in the coil-overs once again. Voila! Everything fit.

(When the actual Skyjacker 2-1/2-inch suspension lift kit for the ’05 Tacoma comes out the fitment problems we encountered will undoubtedly be resolved.)

When we were finished, the front suspension held the Tacoma 2.5-inches higher than stock. This allowed just enough clearance for the 33-inch Swamper Bogger tires we plan running in the jungles, and more than enough clearance for the 32-inch ProComp All-Terrain street tires to get the truck between the university and the jungles of Guatemala.

The rear suspension was considerably easier. It took Chucky and Josh just a few minutes to pull the stock Toyota Tacoma leaf packs apart, insert the Add-A-Leafs, and bolt the packs back together. The new shocks required a little spreading of the lower mounts on the axle housing to fit the Platinum Series shocks’ wider eyes.

Bolstered by the Add-A-Leafs and heavier-duty shocks, the rear was raised nearly three inches. The drawback of the extra leaf is it stiffened the ride considerably — not what you’d want for daily driving unless the bed has a load in it (which it will have) or a bed shell to add a couple hundred pounds.

We’d much prefer a set of nicely tapered leaf springs designed specifically for the application. They will come as suspension manufacturers finish their own prototype work on the new Toyota — and when a set is available, the Maya Hunter will have them installed.

In fact, over the next few months the Maya Hunter suspension will continue to be tweaked until it’s the way we want it. We’ll keep you updated on those changes.

Right now the truck sits a little tail-high and the front coil-overs are adjusted about as far down as possible. The end result is the truck has very little down travel left in the suspension, or suspension droop, and a lot of up-travel. Which is just what we expected with an IFS lift.

The upside is with the ATV trailer and Yamaha Rhino on the hitch the Maya Hunter levels right out, and the towing ride is close to the way we envisioned it at the outset.

As for unladen ride quality up front, it’s pleasant; the new coil-over shocks are valved just right for on- and off-road adventures while carrying the weight of a sturdy winch and bumper.

Speaking of which, next month our focus literally moves to the front where we set the Maya Hunter Tacoma up for self-recovery with the installation of an ARB bumper from Australia and Warn’s Extreme Performance (XP) 9.5-Series winch.

Buy Suspension Products from www.4wheelparts.com.

1. Charles Robinson dives into the front suspension upgrade by removing the factory coil-overs. Craftsman tools, and a nice hoist at 4WD Specialist four-wheel-drive shop, greatly facilitated such undertakings.		2. Skyjacker Platinum Series coil-overs for the earlier model Tacoma (foreground) and Softride replacement springs were the original items selected to provide our 2005 Double Cab with a 2.5- to 3-inch lift. But those parts didn’t quite fit the bill.
3. The final choice on coil-overs for our jungle-running Tacoma were those from the Toyota Tundra full-size pickup, which are rated somewhere around 600 pounds.		4. Josh Hodges, owner of 4WD Specialist, makes initial adjustments on the new coil-overs prior to installation.
5. Skyjacker’s Platinum Plus coil-overs are huge compared to the stock TRD 4x4 offerings that utilize Bilstein’s high-pressure gas shocks. Although the bigger shocks would handle the loads, towing, and extreme use better, they presented a few installation challenges.		6. Our first hurdle was getting the big Skyjacker coil-overs to clear both the axle shafts and the swaybar, which now wraps forward instead of rearward as in previous Tacoma models.
7. Because the Skyjacker coil-over spring was designed to sit at the base of the shock and the factory Toyota spring is mounted mid-way up the shock, we needed a 2-inch-tall spacer to clear the axle shaft to make the new coil-overs fit.		8. Skyjacker custom-milled the spacer for us as a temporary fix for the axle clearance issue. After the spacer was installed, the coil-overs did the job nicely.
9. Josh and Chucky made much quicker work of upgrading the rear suspension than the front. They removed the stock Bilstein shocks and factory leaf springs, using a transmission jack to drop the rear differential just enough to slip the spring packs out.		10. Chucky adds the Skyjacker Softride Add-A-Leaf between the factory leafs and installs a new spring-center bolt to hold the thicker spring pack together. Add-A-Leaf bumps ride height up about 3 inches while stiffening the ride.
11. The factory rear shocks are dwarfed by the Skyjacker Platinum Series BIG GAS Shocks, which are pressurized by nitrogen and can be mounted in any position. They also feature an internal reservoir and two-inch piston bore to keep fluids cool even under severe use.		12. Skyjacker’s Big Gas shocks are stout. The 7/8” chrome-hardened piston shafts will not rust, and the shock body utilizes race-inspired wafer-style valving that can be rebuilt in the field.

 

 

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