2018 Kenworth T680 Wheel Alignment Specifications

As an ASE-certified alignment technician, I know that keeping a Class 8 commercial truck like the 2018 Kenworth T680 tracking straight is entirely different from aligning a standard passenger vehicle. Proper alignment on a commercial rig is critical to maximizing fuel economy, extending steer and drive tire life, and reducing driver fatigue. Below, you will find the alignment specifications, adjustability details, and best practices for the 2018 Kenworth T680.

Quick reference

The following table provides the generally accepted specifications for a 2018 Kenworth T680 (steer axle and tandem drive axles). Keep in mind that heavy-duty trucks often use fractional inches for toe, but they are converted here to degrees for standard machine readouts. Note: Front refers to the steer axle; Rear refers to the tandem drive axles. Caster and SAI apply to the steer axle only.

Note: Heavy-duty steer axles often have a slight left/right camber and caster stagger built-in to compensate for road crown, but base targets should remain within the provided ranges.

Adjustability

Unlike a standard pickup or car, a 2018 Kenworth T680 features a solid I-beam front steer axle and solid tandem rear drive axles. Because of this architecture, factory adjustability is highly limited without adding aftermarket components or performing specialized heavy-duty adjustments.

• Front Caster: Not easily adjustable from the factory. Adjusting caster requires installing angled wedges (shims) between the steer axle and the leaf springs.
• Front Camber: Non-adjustable by traditional means. The factory steer axle is forged with a set camber angle. If camber is out of specification, it typically indicates a bent axle, worn kingpins, or collapsed wheel bearings. In specialized heavy-duty shops, camber can sometimes be corrected by cold-bending the I-beam, but replacing worn parts is always the primary step.
• Front Toe: Fully adjustable. The tie rod cross tube connecting the left and right steering knuckles features threaded ends to adjust total toe.
• Rear Alignment (Thrust Angle): Drive axles are fixed. If the thrust angle or tandem scrub angle is out of spec, it usually means the axle housings are misaligned on the leaf springs or air ride suspension. Adjustments are made by shifting the axles using adjustable torque rods (if equipped) or by loosening the U-bolts and realigning the axle position.

Recommended adjustment hardware

To bring a commercial truck like the T680 back into perfect alignment, you will often need specific hardware:

• Caster Wedges/Shims: Available in increments of 0.5° to 2.0°, these metal wedges are placed under the leaf spring pack to tilt the steer axle and correct caster pull.
• Adjustable Torque Rods: If the drive axles are dog-tracking or generating a bad thrust angle, installing adjustable torque rods (if not already factory-equipped) allows technicians to dial in the drive axle tracking precisely.
• Replacement Kingpin Kits: Since camber and SAI issues are most commonly caused by wear rather than misadjustment, a heavy-duty kingpin replacement kit is often the necessary "hardware" to fix a lean.

Symptoms of bad alignment

With commercial tires costing hundreds of dollars each, identifying alignment wear early is crucial. Look for these tire-wear patterns:

• Feathering on Steer Tires: The edges of the tread ribs feel smooth when you run your hand one way, but sharp the other way. This is a classic sign of incorrect toe-in or toe-out.
• One-Sided Shoulder Wear: If the inside or outside edge of a steer tire is wearing down faster than the rest of the tread, camber is likely out of spec.
• Cupping or Scalloping: Often points to worn suspension components (like shocks) or loose wheel bearings rather than just alignment, but an out-of-balance tire combined with bad toe can accelerate it.
• Dog-Tracking: If you can see the trailer or the tractor's rear end tracking offset from the steer axle in your mirrors, the tandem drive axles have a severe thrust angle issue.

When to align

Heavy-duty trucks require alignments much more frequently than passenger vehicles due to the extreme loads they carry. You should perform an alignment on your Kenworth T680:

• Every 80,000 to 100,000 miles, or annually, as part of a routine preventative maintenance schedule.
• Immediately after replacing steer tires, to protect your investment.
• After any major suspension or steering work, including kingpin replacements, tie rod end replacements, or spring work.
• If the driver reports a persistent pull, an off-center steering wheel, or if you hit a severe pothole, curb, or road debris.

Typical alignment cost

Because aligning a Class 8 truck requires a specialized heavy-duty alignment rack and significantly more labor than a passenger vehicle, costs are higher. A standard 3-axle (steer and tandem drives) alignment typically costs between $250 and $400. If specialized work is needed, such as adding caster shims or adjusting the tandem axles via U-bolts, the cost can easily range from $400 to $700 depending on labor rates and the condition of the undercarriage hardware.

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