5 Fixes for Common Suspension Problems on Kenworth T680

1. Worn Leaf Springs

Leaf springs are the backbone of the T680's suspension system. They're long, curved metal strips stacked together that absorb road impact and support the vehicle's load. Over time, repeated stress causes individual leaves to crack, lose their arc, or break entirely.

Signs you're dealing with worn leaf springs:

• Uneven ride height on one side of the truck
• Visible cracks or separation between leaves
• Excessive body roll when cornering or changing lanes
• Sagging under loaded conditions that weren't there before

The fix involves inspecting each leaf individually for fatigue cracks and checking the U-bolts that clamp the spring pack to the axle. Cracked leaves need replacement. Loose U-bolts need to be re-torqued to spec immediately, as they directly affect axle alignment and handling stability.

2. Worn or Damaged Bushings

Bushings are rubber or polyurethane sleeves that sit at suspension pivot points, cushioning metal-to-metal contact and allowing controlled movement. On the Kenworth T680, bushing wear is one of the most common causes of clunking, wandering steering, and uneven tire wear.

How do you know if suspension bushings are worn on a Kenworth T680?

Worn suspension bushings on a Kenworth T680 typically cause clunking over bumps, a loose or vague steering feel, and uneven tire wear. A visual inspection will often reveal cracking, splitting, or the bushing has shifted out of its housing entirely.

Once bushings wear through, metal components start contacting each other directly. That accelerates wear on the surrounding parts quickly. The fix here is straightforward but time-sensitive:

• Remove and inspect all bushing locations during any suspension service
• Replace any bushing showing cracking, compression set, or visible deterioration
• Check surrounding brackets and pins for wear caused by the failed bushing
• Verify alignment after replacement, as bushing wear frequently pulls alignment out of spec

3. Failing Shock Absorbers

Shock absorbers on the T680 control the oscillation of the leaf spring suspension after road impacts. Without them working properly, the truck bounces, handling becomes unpredictable, and tire contact with the road surface becomes inconsistent.

Worn shocks are easy to overlook because they degrade gradually. Drivers often adapt to the change without realising the truck's handling has slipped well below where it should be. Watch for these indicators:

• Excessive bounce after hitting a bump or road irregularity
• Front-end diving hard under braking
• Cab movement that feels loose or unsettled at highway speed
• Uneven tire wear patterns, particularly cupping or scalloping on the tread

Replacing shocks in axle pairs is the right approach. Replacing only one side creates imbalanced damping and can introduce handling problems of its own.

4. Air Ride System Issues

Many T680 configurations use an air ride suspension system at the rear, where air springs, also called air bags, replace traditional metal springs to provide a smoother, adjustable ride. These systems rely on a constant supply of clean, regulated air pressure to function correctly.

What causes air ride suspension to fail on a heavy-duty truck?

Air ride suspension failures are most commonly caused by leaking air bags, a faulty height control valve, or moisture contamination in the air system. Any of these disrupts the pressure balance, causing the truck to sit unevenly or lose ride quality entirely.

Common air ride problems on the T680 include:

• Air bag leaks from cracked or abraded bag material, causing one side to sit lower
• Height control valve failure, which regulates how much air enters each bag
• Air line fittings that loosen or crack from vibration over time
• Moisture in the air system causing component corrosion internally

Practical tip: If your T680 is sitting lower on one side after being parked overnight, start by checking the air bags and height control valve before assuming a larger system problem. A slow leak is often the culprit and a straightforward repair when caught early.

5. Misaligned Axles

Axle misalignment on the T680 often develops gradually, triggered by hard impacts, worn bushings, or loose suspension hardware. Left uncorrected, it causes accelerated and uneven tire wear, pulls on the steering, and puts extra stress on drivetrain components.

This isn't something you can fix by feel. Proper diagnosis requires an alignment check with the correct equipment for heavy-duty trucks. Here's what the correction process involves:

• Measuring thrust angle, which determines how the rear axle tracks relative to the vehicle's centreline
• Inspecting and replacing any worn components contributing to the misalignment before adjusting
• Re-torquing all suspension fasteners to manufacturer specifications after alignment
• Road testing under load to confirm the correction holds in real operating conditions

Practical tip: Schedule alignment checks after any significant impact, suspension component replacement, or if drivers report the truck pulling to one side. Catching it early prevents tire replacement costs from stacking up across the fleet.

Schedule Suspension Service

Kenworth T680 suspension problems follow predictable patterns, and most of them respond well to early intervention. Staying on top of inspections and acting on the early indicators keeps repair costs manageable and your T680 handling the way it should.

If your T680 is showing any of these symptoms, the team at B&B Truck & Trailer Repair is ready to diagnose and sort it out. Give us a call before a suspension issue turns into a costly breakdown.

For more information about truck repair, read our article on how to tell if you DPF is clogged & needs service.