Track tension problems on a Komatsu D39EX can significantly affect undercarriage life, machine performance, fuel consumption, and overall operating costs. Improper track adjustment is one of the leading causes of premature undercarriage wear and unexpected track derailment.
Many operators focus on engine, transmission, and hydraulic systems while overlooking track tension. However, incorrect track adjustment can create symptoms that resemble travel motor problems, transmission issues, steering difficulties, and power loss under load.
Whether the tracks are excessively loose or overly tight, operating the machine without correction can result in expensive repairs.
Common Symptoms
- Track coming off rollers
- Track derailment
- Excessive undercarriage wear
- Machine feels sluggish
- Poor steering performance
- Reduced travel speed
- Track noise during operation
- Accelerated sprocket wear
- Higher fuel consumption
- Uneven track wear
- Track binding during travel
Main Causes of Track Tension Problems
| Problem | Possible Cause | Severity |
|---|---|---|
| Loose tracks | Grease adjuster leakage | High |
| Track derailment | Insufficient tension | High |
| Excessive wear | Over-tight tracks | High |
| Track binding | Seized components | Medium |
| Uneven wear | Improper adjustment | Medium |
Loose Track Adjustment
Tracks that are too loose can create serious operational problems.
Excessive sag increases the risk of derailment, especially during turning, side-hill operation, and work in rocky terrain.
Loose tracks also increase impact loading on undercarriage components.
Over-Tight Track Adjustment
Many operators mistakenly believe tighter tracks improve reliability.
In reality, excessive tension dramatically increases wear on:
- Track chains
- Rollers
- Idlers
- Sprockets
- Final drives
Over-tight tracks increase resistance and reduce overall machine efficiency.
Track Adjuster Leakage
The hydraulic or grease track adjuster maintains proper track tension.
When seals fail, grease escapes and track tension gradually decreases.
This is one of the most common causes of recurring loose track complaints.
Undercarriage Wear
As undercarriage components wear, track geometry changes.
Even properly adjusted tracks may begin exhibiting tension-related symptoms if wear becomes excessive.
How Track Tension Problems Progress
Track tension issues generally worsen over time.
- Minor track sag develops
- Steering performance changes
- Undercarriage wear accelerates
- Track alignment deteriorates
- Travel resistance increases
- Track derailment risk rises
- Major undercarriage repairs become necessary
Routine inspections can prevent most track-related failures.
How to Diagnose Track Tension Problems
Step 1: Measure Track Sag
Track sag should be measured according to Komatsu specifications.
Visual estimates are often inaccurate and may result in improper adjustment.
Step 2: Inspect the Track Adjuster
Check for:
- Grease leakage
- Damaged seals
- Adjustment cylinder damage
- Improper operation
Grease leakage is one of the most common causes of recurring loose tracks.
Step 3: Inspect Rollers and Idlers
Excessive wear may affect track alignment and tension.
Worn components can create symptoms that resemble adjustment problems.
Step 4: Check Track Chain Condition
Inspect:
- Pin wear
- Bushing wear
- Chain stretch
- Link damage
Excessively worn chains can make proper adjustment difficult.
Step 5: Evaluate Operating Conditions
Track tension requirements vary depending on:
- Mud
- Rock
- Sand
- Forestry debris
Adjustment should consider actual operating conditions.
Most Common Failure Areas
| Component | Typical Failure | Likelihood |
|---|---|---|
| Track adjuster | Grease leakage | Very High |
| Track chain | Wear and stretch | High |
| Front idler | Wear damage | Medium |
| Carrier rollers | Bearing failure | Medium |
| Sprockets | Accelerated wear | Medium |
Common Misdiagnoses
Blaming Travel Motors
Machines with excessive track resistance often appear to have travel motor problems.
Incorrect tension should always be ruled out before hydraulic repairs.
Assuming Tighter Is Better
Over-tightening tracks is one of the most common maintenance mistakes.
Excessive tension accelerates wear throughout the undercarriage.
Ignoring Adjuster Leaks
Minor grease leakage often becomes a major reliability issue if left unresolved.
Track tension will continue decreasing over time.
Repair Solutions
Track Adjustment
- Restore proper sag
- Improve steering performance
- Reduce wear rates
- Improve efficiency
Track Adjuster Repairs
- Replace seals
- Repair grease leaks
- Restore adjustment capability
- Prevent future tension loss
Undercarriage Component Replacement
- Replace worn rollers
- Replace worn idlers
- Repair damaged chains
- Improve alignment
Track Chain Service
- Correct excessive wear
- Improve tracking performance
- Reduce derailment risk
How to Prevent Track Tension Problems
- Check track sag regularly
- Inspect adjusters for leaks
- Monitor undercarriage wear
- Adjust tracks according to operating conditions
- Inspect rollers and idlers routinely
- Repair grease leaks immediately
- Avoid excessive track tension
Proper track tension is one of the most important factors affecting undercarriage life and overall operating cost on the Komatsu D39EX.
Related Diagnostic Guides
- Komatsu D39PX Travel Motor Problems
- Komatsu D65EX Weak Steering Under Load Explained
- Komatsu D65PX Transmission Slipping Under Load
For official Komatsu service procedures and specifications, refer to the official documentation.
Frequently Asked Questions
What happens if Komatsu D39EX tracks are too loose?
Loose tracks increase the risk of derailment, uneven wear, poor steering performance, and accelerated undercarriage damage.
Can over-tight tracks damage the undercarriage?
Yes. Excessive tension increases wear on chains, rollers, idlers, sprockets, and final drive components.
Why do my tracks keep becoming loose?
The most common cause is grease leakage from the track adjuster assembly or worn adjustment components.
Can track tension affect travel performance?
Yes. Incorrect track tension can increase resistance, reduce efficiency, and create symptoms similar to drivetrain problems.
How often should track tension be checked?
Track tension should be inspected regularly, especially when operating in changing terrain conditions such as mud, rock, or forestry environments.
