Caster Wedges for TOYOTA 4 RUNNER E60RG

Caster wedges, also spelt castor wedges and often called leaf spring wedges, are tapered plates fitted between a leaf spring and the axle's spring seat. They tilt the axle by a set number of degrees. On a lifted leaf-sprung rear axle, that tilt realigns the differential's pinion with the tailshaft, helping restore the driveline angles a lift disturbs. On the less common leaf-sprung front axle, a wedge changes caster, which affects steering stability. Use the vehicle search to find caster wedges to suit your E60RG 4 RUNNER.

What Do Caster Wedges Do on a E60RG 4 RUNNER Leaf Spring Axle?

On a leaf-sprung axle, the axle sits on top of or below the leaf spring and is clamped to it with U-bolts. The surface the axle sits on, called the spring seat, sets the angle of the axle housing relative to the spring.

A caster wedge is thicker at one end than the other. Fitted between the spring and the spring seat, it rotates the axle housing slightly forward or backward, depending on which way the thick end faces. Wedges are made in different angles, commonly 1, 2 and 3 degrees, so the amount of rotation can be matched to the correction needed. Once the U-bolts are tightened, the wedge holds the axle at its new angle.

What that rotation achieves depends on which axle the wedge is fitted to. At the rear, it changes the angle of the differential pinion. At the front of a leaf-sprung axle, it changes caster.

E60RG 4 RUNNER Pinion Angle vs Caster: Rear and Front Wedges

The names caster wedge and castor wedge come from their original use on leaf-sprung front axles, where rotating the axle changes the caster angle of the steering. Caster is the backward tilt of the steering axis, and it affects straight-line stability and how the steering returns to centre after a turn.

Most current 4x4 utes and wagons have leaf springs only at the rear, and on a rear axle there is no steering. A wedge fitted to a rear leaf-sprung axle changes the angle of the differential pinion, the shaft where the tailshaft connects to the differential. That angle needs to suit the tailshaft for the driveline to run smoothly. Wedges used at the rear are therefore sometimes called pinion wedges or pinion angle wedges, though they are the same type of part. Front caster correction on coil-sprung and independent front suspension vehicles is handled with arms or adjustable bolts instead of wedges.

Why Pinion Angle Matters on Your E60RG 4 RUNNER

The tailshaft connects the gearbox or transfer case to the differential, with a universal joint at each end. For the tailshaft to turn smoothly, the angles at those two universal joints need to be closely matched. On most conventional tailshafts, that means the differential pinion should sit roughly parallel to the output shaft at the front of the tailshaft.

When the angles do not match, the universal joints speed up and slow down slightly as they rotate, creating a vibration that varies with road speed. Mismatched angles also wear the universal joints faster. A small mismatch may only be noticeable under acceleration, while a larger one can cause vibration across a wider speed range.

Do You Need Wedges After a E60RG 4 RUNNER Leaf Spring Lift?

Often. Raising a leaf-sprung 4x4 increases the distance between the axle and the chassis, which changes the angle of the tailshaft and can change the angle of the axle housing as well. The pinion may then no longer sit at the right angle relative to the tailshaft.

A common sign is a vibration that appears under acceleration, at certain road speeds or when the vehicle is loaded, after a lift has been fitted. Wedges are a common way to correct it by rotating the pinion back into line. The need varies with the vehicle, the lift height and the spring design, so the driveline angles should be measured rather than assumed.

1, 2 or 3 Degree: Which Wedge Does Your E60RG 4 RUNNER Need?

It depends on the measured angle change, not lift height alone. Two vehicles with the same lift can need different corrections, because spring design, tailshaft length and load all affect the driveline angles.

The angles are measured with an angle finder at the transfer case or gearbox output, along the tailshaft and at the differential pinion. Comparing those readings shows how much the pinion needs to rotate, and which way. A workshop can then select the wedge angle that brings the pinion closest to the correct position. Choosing a wedge by lift height alone risks over-correcting or under-correcting, which can leave the vibration in place or create a new one.

E60RG 4 RUNNER Wedges and Axle Wrap

Under hard acceleration or braking, leaf springs can twist into an S-shape as the axle tries to rotate, an effect called axle wrap. It changes the pinion angle momentarily and can cause vibration or axle hop. Lifted vehicles with longer or softer springs can be more prone to it.

Wedges set the static pinion angle when the vehicle is at rest. They do not stop axle wrap, which is a separate issue controlled by spring design and, on some vehicles, by additional components such as torque arms. If driveline vibration only appears under heavy acceleration or when towing, axle wrap may be part of the cause.

Wedges and E60RG 4 RUNNER Front Leaf-Sprung Axles

On 4x4s with a leaf-sprung front axle, a lift can reduce caster by rotating the axle as the springs change shape. Reduced caster can make the steering feel light, less stable at speed and slower to return to centre. A wedge fitted between the front spring and axle rotates the axle back to restore caster.

Rotating a front axle also changes its pinion angle, so on a front axle with a driveshaft, the caster correction and the pinion angle need to be balanced. This is one reason front leaf axle corrections should be measured and set by a workshop experienced with leaf-sprung 4x4s.

Fitting E60RG 4 RUNNER Caster Wedges: An Overview

Fitting wedges involves supporting the vehicle and axle securely, removing the U-bolts, separating the axle from the spring just enough to insert the wedge, and refitting the axle. The wedge must face the correct direction, with its thick end positioned to rotate the axle the way the measurement requires. Fitting it backwards doubles the error rather than correcting it.

Because a wedge adds height between the spring and axle, longer U-bolts may be needed so they still engage the full thread of their nuts. New U-bolts are commonly recommended when the originals are removed, since used U-bolts can stretch. The spring centre bolt must locate correctly through the wedge. All fasteners must be tightened to the specified torque, and the U-bolts rechecked after the first few hundred kilometres. A qualified suspension technician should carry out the work.

Checking the Result on Your E60RG 4 RUNNER

After fitting, the driveline angles should be measured again to confirm the correction, and the vehicle road tested at the speeds where vibration occurred. If vibration remains, other causes should be checked, including worn universal joints, an unbalanced tailshaft, a worn centre bearing on two-piece tailshafts, and wheel balance. On a front leaf axle, a wheel alignment is required after fitting a wedge, since it changes caster.

Find the Right E60RG 4 RUNNER Caster Wedge with Formula 4x4

Leaf sprung 4WDs that sit higher often need caster wedges to bring the angles back, and they're found in our alignment parts range.

Start by having the driveline angles measured after your lift, to confirm how much the pinion needs to rotate and in which direction. Confirm whether the wedge is for a rear or front leaf-sprung axle, and check whether longer U-bolts will be needed. Search by your E60RG 4 RUNNER to find 4x4 caster wedges to suit it. If you are unsure what your 4x4 needs, contact the Formula 4x4 team.