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Solid Axle Swap: An SAS Conversion For A 1998 Toyota Tacoma

Posted in How To: Transmission Drivetrain on July 11, 2017
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The grass is always greener on the other side of the off-road fence. We spend a lot of time and money modifying our rigs, changing what OEM designers and engineers spent years refining and fine-tuning. Purpose built, purpose driven. That’s how a good many 4x4 owners look at their rides.

A great example of such thinking is those who go through the effort of swapping out their 4x4’s independent front suspension (IFS) for a straight-axle. IFS works wonderfully to smooth out the ride as each front wheel moves independently from the one on the opposite side, but many wheelers see IFS as a hindrance, not a help, when smooth roads give way to big rocks and deep ruts—when strength becomes more important than weight, or the need for greater suspension articulation outweighs a car-like ride. For many, a solid axle up front rules off-road.

Toyota 4Runners and Tacomas are a perfect example of that way of thinking for many owners who live to off-road. When Toyota dropped solid axles in the U.S. models with the introduction of the IFS-equipped ’86s, many die-hard Toyota off-road aficionados wept. Then they wiped away the tears and figured out how to convert the 4x4s from IFS to solid axle.

Castle started the axle swap using an ’83 Jeep Wagoneer front axle assembly (non-vacuum 4WD disconnect) with a 6-on-5.5-inch bolt pattern—same as his Tacoma. It cost all of $125 from a local salvage yard, including the fancy white steel wheels.

Solid axle swaps (SAS) are relatively simple in concept. However, they require deft skills with a plasma cutter and welder, along with the necessary pre-planning so one has all the right parts to make the conversion worthy of the time and money spent making it happen. Finding the SAS kits and parts is easy now that four-wheelers have been doing them for nearly three decades. We found that out when Casey Castle, a tech at Dunk’s Performance in Springfield, Oregon, decided he wanted take his ’98 Tacoma to a new level of off-road performance.

His third-hand Tacoma sat atop a six-inch IFS lift, but it lacked what he desired in articulation and travel. He went parts shopping at a local salvage yard to find a front axle from under an ’83 Jeep Wagoneer along with a steering box from an early ’90s Tacoma as the base components for the swap. Then he pieced together the rest of the conversion parts from Sky’s Off-Road Design, Trail-Gear, and Tom Wood’s Custom Drive Shafts to turn his Toy into a reliable, long-legged, mud-and-rock-running trail rig that’s still quite suitable as a daily driver.

We followed Castle’s Tacoma SAS conversion from beginning to end, then went for a trail ride on its inaugural off-road outing. Doing an SAS on one of these first-gen Tacoma trucks proves the grass is definitely greener and better tasting on the solid axle side of the off-road fence. Read on for the highlights of the conversion.

The suspension and frame modification parts were sourced from Sky’s Off-Road Design (SORD), including SORD’s six-leaf, four-inch-lift spring packs (PN Sky-Tac-004). The spring-over-axle setup retained the six-inch lift that was already under the ’98 Tacoma.
Nothing under the front was going to be reused, so Castle dove in with a plasma cutter to remove the IFS as one unit by cutting off the mounting brackets flush with the frame. This keeps the whole shebang intact for someone wanting to convert a 2WD Tacoma to 4WD.
A tip to make the installation of the new parts easier, and to keep the frame integrity intact, is to cut off the OEM brackets with the plasma cutter parallel to the frame.
Having a forklift made it super simple to cut and drop the entire front suspension in one tidy chunk instead of trying to balance it on floor jacks.
SORD’s frame reinforcing plates are made from 1/4-inch steel and are CNC machined for a very precise fit over the Toyota framerails. The plates are easy to line up, using holes on the frame to match those on the plates. SORD has very good instructions and photos on their website on the entire SAS project.
The framerails were cleaned and smoothed before installation of the reinforcement plates, which are needed to handle the loads placed on them by a solid axle setup. The driver-side plate was held in position, and the steering box holes were marked and reamed out so the anti-crush sleeves that come with the SORD kit could be welded in place.
We selected a third-gen Toyota pickup IFS steering box for this swap. It’s an easy find, inexpensive, and a perfect fit for an SAS.
It’s important the anti-crush sleeves for the steering box bolts are flush with the outside of the framerail before tacking them into position. The sleeves are ¾-inch OD. We made sure the steering box aligned perfectly with the mounting holes each step of the way.
After we had the sleeves in place, the reinforcement plates were welded to the framerail. SORD’s plates wrap around the frame for added support. The voids cut in the plate provided additional welding surface for added frame strength.
After the reinforcement plate on the driver side of the frame was welded on both sides and painted it was ready to have the steering box bolted into place.
Out with the old. We removed the OE steering shaft/coupler and the through-floor mounting plate/boot/seal. The plate was held in place by 10mm bolts. It took a light hit with a hammer from the firewall side to pop the plate loose from the floor.
The OE steering plate and shaft assembly were replaced with components (shaft, firewall plate, seal, and couplers) from Trail-Gear. The Tacoma SAS Steering Kit includes all the needed parts. The new shaft angles out to the front to match the third-gen pickup IFS steering box. The shaft to the OEM rack-and-pinion pointed almost straight down.
We coated the firewall plate with a generous amount of RTV sealant before installing to seal it up against deeper mud and water.
In some instances, the IFS steering shaft will have to be cut shorter so it doesn’t interfere with the steering coupler U-joint. Castle nipped off about a 1/2-inch from the steering box we used for this SAS conversion. Tip: Tighten the locking nuts once the set screws are tight, then check them once a month to ensure they remain tight.
We moved to the front of the frame and cut off 2 3/4 inches so the SORD 2x3-inch steel tube crossmember that holds the front spring shackles could be welded on along with the angled end gussets. Tip: Use the supplied end gussets to mark the cuts on the OE frame ends, and make sure the new crossmember is square to the frame and centered.
SORD offers several different lifts and spring offsets for this swap. Castle chose the SORD four-inch-lift, six-leaf springs that have the spring center pin located about two-inches forward of the stock location. This provided a longer wheelbase, increased approach angle, softer front suspension impacts, and allows running taller tires without cutting the rear of front fender wells.
With the front of each spring bolted into the SORD front crossmember, and the Waggy axlehousing square to the frame, we positioned the rear shackle buckets so the spring eyes were slightly forward when the axle was at full droop. Castle then used a plasma cutter and grinder to get the shackle bucket frenched into the framerail. Note the hanger bucket’s position: tight to the rear of the body mount support and tight against the body mount bolt.
An SAS like this requires converting to a high-steer system to clear the leaf springs. We used a Reid Racing steering knuckle (PN D44001CR) mated to a 50 1/2-inch high-steer tie rod from SORD along with an ARP stud kit. We also used an SORD pitman arm because it doesn’t place any side load on the steering box sector shaft.
Another necessary change was removing the OE hydraulic lines from the power steering pump and replacing them with the hoses in the Trail-Gear Tacoma power steering hose kit (PN 130317-1) for the 2.7L that lead to/from the IFS steering box.
To position the shock hoops requires having the truck sitting at ride height. Then the SORD hoops can be tacked in place and measurements taken to order the correct shocks for maximum suspension travel.
Casey used a wire brush and spray paint to clean up the Waggy front axlehousing. The rotors were turned, the ball joints and seals replaced, and the differential rebuilt with Yukon 4.88:1 gears and an ARB Air Locker.
The SAS required a new front driveshaft. Our suggestion is to call Tom Wood’s Custom Drive Shafts because the company can lead you through all the measurements to build the perfect setup. This is one area you don’t want any weakness or miscalculations. Do it right the first time.
The Tacoma SAS requires using a rear-sump oil pan. We used one lifted from a 3RZ Toyota T-100. Another recommended option is installing a Trail-Gear transfer case skidplate (PN 120198) to protect the vitals while being cut perfectly to accommodate our Tom Wood’s driveshaft’s steeper angle.
Our last step before hitting the road was to put the Tacoma on the computerized alignment rack at Dunks Performance.
We hit the trail hard and found out the time and money invested to swap the Wagoneer straight-axle into the Tacoma was everything we’d hoped for with tons of suspension travel and great trail manners. The wheelbase went from 121.9 inches to 124 inches, setting up the 35-inch BFGs so they cleared the stock inner fenders—even while turning under full compression.


Fresno, CA 93727
Renton, WA 98057
Tom Wood's Custom Drive Shafts
Dunks Performance
Sky’s Off-Road Design

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