How to Spot Wear in Excavator Swing Motors and Swing Bearings Before They Cause Major Failure

When an excavator fails, 70% of the time the operator blames the final drive, the pump, or the hydraulics.But the truth is… one of the most expensive and catastrophic failures on any excavator comes from the swing system.

The swing motor and swing bearing (slew ring) quietly handle massive loads every single day:

• Lateral forces

• Shock loads

• Rotational torque

• High-pressure hydraulic spikes

• Dynamic weight shift from boom + dipper + bucket

• Operator-induced stress (fast swings, sudden stops, uneven loading)

If these components start wearing out and you don’t catch it early, your excavator can face:

• Complete upper-structure collapse

• Gear teeth failure

• Irreversible bearing damage

• Broken pinion gear

• Excessive backlash

• Dangerous machine instability

• Repair bills easily exceeding R150,000–R300,000

This blog shows you exactly how to detect early warning signs — before the failure destroys your machine — and why Used OEM swing components from Vikfin are essential for long-term reliability.

1. Understanding the Swing System (Why It Works So Hard)

The swing system includes three core components:

1. Swing motor

Converts hydraulic pressure into rotational torque.

2. Swing gearbox (reduction gear)

Reduces RPM and increases torque to drive the pinion.

3. Swing bearing (slew ring)

A massive bearing that supports the entire upper structure while allowing rotation.

These components face extreme loads:

• Rotational torque

• Side loads from digging

• Shock loads when swinging full buckets

• Asymmetric loads on slopes

• Abrupt operator inputs

• Wear from contamination and poor lubrication

Because of the load complexity, small wear becomes big damage fast.

2. Early Signs of Swing Motor Wear

Catching swing motor wear early saves the gearbox and slew ring.

A. Jerky or uneven swinging

Hydraulic inefficiency, worn motor plates, damaged pistons.

B. Slow swing speed

Loss of hydraulic pressure, internal bypassing, worn seals.

C. Excessive heat

Indicates bypassing or damaged internal components.

D. Buzzing or whining sounds

Loose tolerances, deteriorated bearings, or worn oscillating plate.

E. Swing drift

Machine swings slightly even when controls are neutral — a sign of internal leakage.

F. Delayed response when operator moves joystick

Pressure is leaking past internal components.

These symptoms usually mean the following parts are wearing out:

• Valve plate

• Cylinder block

• Pistons

• Bearings

• Swash plate

• Rotating group

• Motor seals

If caught early, repairs are simple.If ignored, the failure spreads to the gearbox and slew ring.

3. Early Signs of Swing Bearing Wear

Failing to detect swing bearing wear is one of the most expensive mistakes in the industry.

Watch for:

A. Upper structure movement (sway)

If the house rocks when you start digging, the slew ring has play.

B. Vertical play or “lift”

If the upper structure lifts when swinging, the bearing is worn.

C. Grinding sounds during rotation

Metal-on-metal contact inside the bearing.

D. Uneven swing resistance

Flat spots on the raceway or insufficient grease.

E. Excessive grease leakage

Indicates internal seal failure.

F. Metal flakes in grease

A major red flag — indicates internal bearing damage.

G. Abnormal swing backlash

If the machine overshoots during quick swings, you likely have gear wear.

4. The Domino Effect of Ignoring Swing Wear

A worn swing motor causes:

• Excess heat

• Contamination

• Gearbox wear

• Pinion gear damage

A worn swing gearbox causes:

• Tooth rounding

• Backlash

• Metal contamination

A worn slew ring causes:

• Cracked raceways

• Lost load-bearing capability

• Complete upper-structure failure

All three are linked.A failure in one often destroys the other two.

And here’s the scary part:This is one of the few excavator failures that can be fatal.

A collapsed slew ring can cause a machine to topple or lose the boom.

5. Professional Tests You Can Do On-Site

You don’t need a workshop to catch early problems.These tests can be done on any job site.

A. The "Upper Structure Lift" Test

1. Boom up

2. Track frame flat

3. Rotate house slightly left and right

If the house visibly lifts, the bearing is worn.

B. The “Swing Backlash” Test

Slowly swing left → stop → swing right → stop.If the machine “lags” or “overshoots,” you’re losing gear integrity.

C. The “Grease Condition” Check

Remove a small amount of slew ring grease:

If you see:

• shiny flakes → bearing damage

• grey paste → metal wear

• black streaks → burnt grease from heat

Your bearing is failing.

D. The “Drift Test”

Start machine → put swing control in neutral.If the house swings even slightly → internal motor leakage.

E. The “Temperature Gun” Test

After operating, use an infrared thermometer.Swing motor or gearbox hotter than other hydraulic components = internal wear.

6. Why Cheap Aftermarket Swing Components Are a Disaster

Cheap swing motors and slew bearings fail because they have:

• Incorrect heat treatment

• Poor-quality steel

• Weak gear hardness

• Loose tolerances

• Insufficient bearing load ratings

• Poor internal lubrication channels

• Zero factory testing

• Unknown lifespan

Failures are sudden, catastrophic, and expensive.

This is one area where aftermarket parts are particularly dangerous — not just costly.

7. Why Used OEM Swing Motors and Bearings from Vikfin Are the Smarter Choice

Used OEM swing components are engineered for:

• Precise tolerances

• Correct hardness

• Exact gear profiles

• Maximum load capacity

• High-cycle fatigue durability

• Full compatibility with your machine

Vikfin’s used OEM components undergo:

• Inspection

• Cleaning

• Tolerance measurement

• Grease/contamination check

• Load testing (where applicable)

• Rotation smoothness assessment

• Seal verification

You get OEM quality at a fraction of new OEM price, with far superior performance and reliability compared to aftermarket.

8. The Real Cost of Swing Failure in South Africa

A typical major swing failure costs:

• Swing motor failure: R25,000–R55,000

• Swing gearbox failure: R30,000–R80,000

• Slew ring failure: R70,000–R150,000+

• Labour: R8,000–R20,000

• Downtime (per week): R10,000–R40,000

Total potential damage: R150,000–R300,000+

A used OEM swing motor from Vikfin?R15,000–R35,000A used OEM slew ring?R25,000–R70,000

The math is simple:OEM saves your machine.Aftermarket destroys it.

9. When to Replace and When to Repair

Replace immediately if:

• There is vertical play

• The house lifts during swinging

• Teeth are rounded

• There’s major metal contamination

• Motor has severe internal scoring

Repair or replace seals if:

• Minor leakage

• Minimal wear

• Small backlash

• Grease contamination is low

Re-grease if:

• Wear is minimal

• No metal contamination

• Rotation is smooth

10. Final Advice: Swing Components Are Not “Optional” Maintenance

Swing motors and bearings are among the most abused components on an excavator.

The key to long machine life:

• Inspect often

• Grease properly

• Listen for changes

• Don’t ignore early wear

• Don’t gamble on cheap parts

Used OEM swing components from Vikfin ensure your excavator stays safe, strong, and profitable — even under the toughest South African working conditions.

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