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Solid-Axle Swap: Toyota 4Runner

Driver Front Side View
Ben Stewart | Writer
Posted July 8, 2000

Part 2: trail test

Step By Step

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  • Notice the weld-on front hanger bracket and Hy-Steer setup with FJ80 tie rods. This axle is a special reverse-rotation FJ80 model with 4.88:1 gears and a Detroit Locker covered by an All-Pro diff guard. Not visible are Marlin Crawler's new Marfield birfields. The new Marfields are substantially stronger than the previous versions and should be a fairly bulletproof upgrade for solid-axle Toyota owners.

  • All-Pro has rear suspension for pickups as well as 4Runners to match the front axle conversion. The 4Runner suspension for the 4-inch conversion uses a 1.5-inch coil spring combined with a 2.5-inch billet spacer, rod end-equipped adjustable upper control arms, and Johnny Joint-equipped lower arms. Though the Panhard bar on this vehicle was relocated, the system will include an adjustable Johnny Joint bar.

  • When RTI testing on a 20-degree ramp, it's easy to see how much more articulation the 4Runner has after the solid-axle swap. The actual score was boosted about 400 points.

  • In either of these situations, an IFS Toyota (or anything else IFS) would certainly have wheels hanging in the air fighting for traction. With the locked solid-axle suspension, we were able to traverse the terrain in a controlled manner without spinning a tire.

  • Aired down to midteen psi, the 285/75R16 Yokohama Geolander M/Ts were surprisingly sticky on the rocks. Though the tires are 33 inches tall, the Mickey Thompson Challenger wheels are 16 inches, which makes for less sidewall than on a 33x12.50-15 setup. This lower-profile sidewall is a slight compromise on the trail but noticeably improves handling on the street--perfect for our dual-purpose 4Runner. FW

Last month, we covered the installation of the All-Pro Off Road solid-axle swap conversion system on our '91 Toyota 4Runner. After mounting up some fresh 16x8 Mickey Thompson by ALCOA-forged Challenger wheels and 285/75R16 Yokohama Geolander M/T tires, we ramped the new suspension for a comparison to the stock IFS. The stock IFS ramped in the mid 400s. With the new suspension our score jumped to mid 800s on a 20-degree ramp. While this is not quite the "magic" 1,000, we never intended this 4Runner to be the ultimate rock buggy. The goal of this vehicle buildup is to have a competent trail vehicle that is still comfortable and streetable enough to drive daily.

As a daily driver, this '91 4Runner is quite pleasant. The 4.88:1 gearing is well matched to the 33-inch-tall 285/75R16 tires, and the coil-sprung 4Runner rear suspension rides a bit softer than a pickup of the same vintage. We found handling with the new tires and the Hy-Steer setup made us forget all about the typical tradeoffs. However, the true test for our newly solid-axle-swapped vehicle is on the trail.

We tackled Shredder Canyon near Palmdale, California, on two separate occasions and found the additional traction and articulation of the solid frontend to be a huge asset over this type of terrain. On our first run, we actually had two well-set-up IFS Toyotas on the trail with us. Although both vehicles were able to finish the trail, their limited wheel travel made choosing the easiest line imperative and driving less elegantly a fact. Additionally, one owner told us he had not installed a front locker in his IFS because of durability issues.

Without a front locker and serious wheel travel, challenging four-wheeling can lead to spinning tires and broken parts.

With careful driving, our solid axle 4Runner was able to tackle most any obstacle on the trail with ease. Since we were only running 33-inch tires, we kept tire pressure around 13 psi in order to maintain decent ground clearance.

At that pressure, the Yokos gripped the rocks quite well; however, if we were to make a habit of this type of 'wheeling with our 4Runner, a swap to the taller 6-inch spring packs and 35-inch tires would keep the body and drivetrain at a safer distance from the decomposed granite. All Pro had luckily outfitted the rig with its nerf bars, bumpers, and rear quarter-panel guards so the body emerged from the trail with (almost) no body damage.

Overall, this is a very balanced dual-purpose vehicle. It can be a comfortable daily commuter all week long and a fairly hard-core family four-wheeler on the weekend. For an all-out trail Toyota, All Pro's 6-inch suspension with 35-inch tires would probably ramp in the mid 900s. And a 4Runner equipped with lockers and a Marlin transfer case would certainly give anything built in Toledo a run for its money.


Yokohama Tire Corporation
Fullerton, CA 92831
Marlin Crawler
Fresno, CA 93703
All-Pro Off Road
Mickey Thompson Performance Tires & Wheels
Corona, CA 92881