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4x4 Truck Steering System Parts - Steering Theories

Jerrod Jones | Writer
Posted December 1, 2005
Photographers: Alan Huber, Courtesy Of Borgeson

Control All That Truck!

The steering system is probably the most important component of your vehicle to have working flawlessly. And unfortunately, it's probably one of the most ignored systems on modified 4x4s today. We want to help change that. It's easy to get caught up with all the solid axle swaps, locker installs, spring-over conversions, electrical steroids, and custom fabbing we write about. You want the big tires, the lift, the axles, and the motor to push it all, but what about trying to control that three-ton harbinger of terror? You need to be able to properly maneuver it via a well-working (per application) steering system.

Think you know enough about your steering? Maybe you do, but maybe you're not sure if you have rag joints or U-joints on your steering shaft. Ever thought about the caster on your front axle? What about the fact that the inside wheel is at a greater angle than the outside wheel in a turn, or how far off of an ideal Ackerman angle is your steering setup? Have you even heard of an Ackerman angle?

There are many variations of what we're showing you, as well as some one-off setups that probably contradict some of what we tell you, but this will pertain to the majority of us. Read on and we'll steer you straight.

The Hard Parts


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Rack-and-Pinion: A rack-and-pinion steering setup is typically found on independent suspension applications. It consists of a geared shaft (similar to a pinion gear) that moves along a geared track. The pinion gear turns radially, moving the geared track back and forth, moving tie rods that are attached to the rack.

Steering Shaft: The steering shaft joins the steering column to either the steering box or rack-and-pinion. It usually has some type of slip joint built in to absorb shock and compensate for different distances between the steering box and the column. To allow angled movement (because it is almost never a straight shot between components) the shaft usually has some type of joint such as a rag joint or universal joint at both ends.

Power Steering Box (Recirculating Ball): The typical four-wheel-drive steering box is a recirculating ball type that has a worm geardrive to help magnify a driver's input to direct steering linkage one way or another. The steering box gets input from a steering shaft and outputs work through a splined sector shaft. Steering boxes are used in both solid-axle steering systems and on independent suspension setups.

Pitman Arm: The pitman arm moves radially around the sector shaft of the steering box in a single plane. Either a drag link or some type of connecting rod is installed on the other end of the pitman arm, with the pitman arm rotating in an arc, turning the wheels back and forth via the drag link. Dropped pitman arms lower the drag-link mounting point, just as the name implies. These are normally deemed acceptable in most applications and are sold with many suspension systems, but you should realize what is happening when you elongate the distance in between the rotating sector shaft and the tie-rod end of the drag link. The farther away the drag link mounts from the sector shaft, the more sheer force is being put on the sector shaft, and subsequently the more wear you put on the steering box.

Idler Arm: An idler arm is used in IFS steering setups and sometimes in solid-axle steering setups. The idler arm holds one side of a connecting rod that joins to the pitman arm on the opposing side. Tie rods connect to the centerlink and give congruent motion to both knuckles in an IFS configuration. On a solid-axle steering system, using an idler arm is a good way to reduce stress on the sector shaft of a steering box. In a conventional crossover steering setup, the drag link is connected to the pitman arm, putting a massive amount of leveraged stress on the sector shaft whenever force is applied to the drag link. When using an idler-arm setup, the drag link connects to the centerlink, which is attached at both ends to the idler arm and pitman arm. The centerlink is only allowed to move from side to side and therefore puts minimal stress on the sector shaft, preventing premature steering box failure.

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