Finally, a crossover conversion for better steering geometry
Toyota designed the steering system on its straight-axle trucks and 4Runners to be reasonably strong and reliable. When used with stock or slightly larger-than-stock tires, the stock system will provide many thousands of miles of reliable service. If the truck has been lifted significantly or is used for hard-core trail running, however, an upgrade is worth serious consideration.
The stock steering system uses a relatively short trailing drag link that moves perpendicular to the axle and connects to a J-shaped steering arm that is attached to the top of the driver-side knuckle. This stock drag link sits at a near-horizontal angle and is not adjustable in length. Whenever a suspension lift is added, the angle of the drag link increases. For minimal lifts of up to 3 inches, this is not a problem because the original turning radius can be maintained.
When the lift exceeds 3 to 4 inches, however, the stock drag link is no longer long enough to provide full lock-to-lock turning capability. The left-hand turn radius is not affected, but the right-hand turn radius is increased because the drag link is not long enough to push the knuckle arm to its full travel. Running larger tires with the lift also stresses the J-arm during driver-side suspension droop. This often eventually leads to fatigue and fracture of this steering arm-clearly not a good thing.
A company called 4x4 Labs manufactures a crossover-style steering kit that ends these problems. The conversion requires the use of an '86-'95 Toyota IFS steering box. Pre-'86 straight-axle trucks require that some new holes be drilled in the frame to convert to the newer steering box. IFS trucks converted to straight-axle will already have the box in place. The kit provides replacement steering arms to go on each front axle knuckle and a pitman arm to fit the IFS box.
Another issue with the stock axle components is the weak tie rod that sits in a low, vulnerable position in front of the axle. The 4x4 Labs steering arms position the tie rod above and behind the axle, out of harm's way. The new drag link attaches to the pitman on the IFS steering box and to the top of the new passenger-side arm. The tie rod attaches and steers from behind. Similar setups can be found on Land Cruiser FJ80s and late-model Land Rovers. The supplied tie rod and drag link are constructed of 11/44-inch-wall (or heavy-wall) mandrel-drawn steel tubing that is cut and threaded to employ GM 1-ton ends, 71/48-inch spherical rod ends or 23mm FJ80 ends.
For custom applications, the steering box can be moved further forward without the tie rod and drag link interfering with each other. A properly designed set of steering arms should take into account the Ackermann Principle. Ackermann steering geometry involves steering linkage designed to allow the inner tire to steer in a tighter radius than the outer tire when making a turn.
The 4x4 Labs steering arm sets are engineered to match the wheelbase and track width of specific Toyota models. The arms are available for a number of Toyota truck, 4Runner, and Land Cruiser axles. 4x4 Labs also manufactures its arms in multiple height offsets to accommodate varying degrees of lift.
Check out the photos below to see some details on the install and configuration of a 4x4Labs steering system on an '86 4Runner used for extreme trail duty.