The undercarriage is one of the most expensive wear areas on a tracked excavator. Correct track tension, clean running gear and early attention to rollers, idlers, sprockets and final drives can greatly extend component life.
Track-sag dimensions, final-drive oil specifications, bolt torques and inspection limits vary by make, model and serial range. Use the correct operator or workshop manual for exact figures.
1. Main Undercarriage Components
A typical tracked excavator uses:
- Track chains or rubber tracks
- Track rollers
- Carrier rollers
- Front idlers
- Drive sprockets
- Track adjusters
- Recoil springs
- Travel motors
- Final drives
2. Steel Tracks and Rubber Tracks
Excavators may use:
- Steel track chains with shoes
- Rubber tracks
- Road-liner or rubber-pad arrangements
Each type has different wear and tension requirements.
3. Why Track Tension Matters
Tracks that are too tight can increase wear on:
- Track pins and bushes
- Rollers
- Idlers
- Sprockets
- Final-drive bearings
Tracks that are too loose can derail or jump teeth.
4. Check Track Sag Correctly
The correct measuring procedure varies between machines.
The manual may specify:
- Machine position
- Track lifted or on ground
- Measurement location
- Required sag
Mini excavators, large excavators, steel tracks and rubber tracks can all require different settings.
5. Grease Track Adjusters
Many excavators use grease pressure to move the idler and tension the track.
The adjuster normally includes:
- Grease fitting
- Adjuster cylinder
- Recoil spring assembly
6. Releasing Track Tension
Track adjusters can contain grease under very high pressure.
Never stand directly in front of a grease-release fitting. Loosen only by the amount and method specified in the workshop manual.
7. Track Too Tight After Greasing
If too much grease has been added:
- Follow the approved pressure-release procedure
- Move the machine as specified
- Recheck sag
Do not attempt to force the idler backwards mechanically.
8. Track Keeps Going Loose
Possible causes include:
- Grease leaking from adjuster
- Worn adjuster seals
- Damaged grease valve
- Track chain wear
- Idler movement problem
9. Track Rollers
Bottom rollers carry most of the machine weight.
Check For
- Oil leaks
- Flat spots
- Excessive flange wear
- Loose bearings
- Seized rollers
10. Carrier Rollers
Carrier rollers support the upper section of the track chain.
A seized or badly worn carrier roller can accelerate chain wear.
11. Front Idler
The idler guides the track and forms part of the tensioning system.
Inspect
- Side wear
- Oil leakage
- Bearing play
- Guide wear
- Free movement in track frame
12. Recoil Spring
The recoil spring allows the idler to move backwards when debris or shock loads enter the track.
A recoil spring stores enormous energy. Do not dismantle the spring assembly without the exact workshop procedure and correct equipment.
13. Drive Sprocket Wear
Worn sprocket teeth may become:
- Sharp
- Hooked
- Unevenly worn
Worn sprockets and worn chain components accelerate each other’s wear.
14. Track Chain Wear
Steel chains wear at:
- Pins
- Bushes
- Links
- Rail surfaces
As pins and bushes wear, track pitch effectively increases.
15. Pin and Bush Wear
Symptoms include:
- Loose track
- Poor sprocket engagement
- Hooked sprocket wear
- Excess chain movement
16. Track Shoe Wear
Inspect:
- Grouser height
- Bent shoes
- Cracks
- Loose shoe bolts
Use the correct bolt torque and tightening procedure.
17. Rubber Track Inspection
Check rubber tracks for:
- Deep cuts
- Exposed steel cords
- Missing drive lugs
- Sidewall cracking
- Chunking
18. Rubber Track Derailment
Common causes include:
- Track too loose
- Worn idler or sprocket
- Debris packed into undercarriage
- Sharp turning on rough ground
- Incorrect track size
19. Keep the Undercarriage Clean
Mud, clay, stones and frozen material can pack around the track frame.
This can:
- Increase track tension
- Damage seals
- Accelerate wear
- Cause derailment
20. Operating Technique Affects Wear
Undercarriage life can be reduced by:
- High-speed travel
- Constant sharp turning
- Working sideways on steep slopes
- Travelling long distances unnecessarily
- Allowing tracks to spin
21. Travel Motors
The travel motor converts hydraulic flow into rotary drive.
Possible symptoms of a travel-motor problem include:
- One side weak
- Machine veers
- Motor noise
- Motor overheating
- Hydraulic leakage
22. Final Drives
The final drive reduces travel-motor speed and increases torque to the sprocket.
It normally contains:
- Planetary gears
- Bearings
- Gear oil
- Seals
23. Check Final-Drive Oil
Final-drive oil should be checked and changed at the interval specified by the manufacturer.
Check For
- Correct oil level
- Metal particles
- Milky oil
- Burnt smell
- External leaks
24. Correct Plug Position
Many final drives use the same plugs for filling, level checking and draining depending on sprocket position.
Rotate the drive only as instructed in the operator or workshop manual.
25. Final Drive Oil Leak
Leaks may occur from:
- Duo-cone/floating seals
- Hub seals
- Drain/fill plugs
- Case joints
Low oil can rapidly destroy planetary gears and bearings.
26. One Track Is Slower Than the Other
Possible causes include:
- Track tension difference
- Brake dragging
- Travel motor wear
- Final drive mechanical fault
- Control valve problem
- Pump flow problem
Do not condemn the travel motor until hydraulic flow and pressure are checked.
27. Excavator Pulls to One Side
Check:
- Track tension
- Undercarriage binding
- Travel speed setting
- Hydraulic pressures
- Travel motor case drain where specified
28. Noise From Final Drive
Possible causes include:
- Low oil
- Bearing wear
- Planetary gear damage
- Contaminated oil
Stop and investigate unusual grinding or knocking before major failure occurs.
29. Routine Undercarriage Inspection
- Clean accumulated mud and debris.
- Check track sag.
- Inspect rollers and idlers.
- Inspect sprocket teeth.
- Check track shoes/rubber tracks.
- Look for final-drive oil leaks.
- Check final-drive oil at service interval.
- Listen for abnormal travel noises.
30. Undercarriage & Final Drive Checklist
| Area | Check |
|---|---|
| Track tension | Set to model-specific specification. |
| Rollers | No leaks, seizure or excessive wear. |
| Idler | Moves correctly and has no excessive play. |
| Sprocket | Teeth not hooked or badly worn. |
| Track chain/rubber | No excessive wear or structural damage. |
| Adjuster | Holds tension without grease leakage. |
| Final-drive oil | Correct level and condition. |
| Travel | Both sides pull evenly. |
| Manual data | Correct sag, oil and torque specifications used. |
Related Agrimanual Manuals
Track tension, final-drive oil, travel pressure tests and overhaul procedures are excavator-specific.
- Search Agrimanual excavator workshop manuals
- Search Agrimanual final-drive and travel manuals
- Request a manual if your machine is not listed
Frequently Asked Questions
How tight should an excavator track be?
Use the exact track-sag measurement in the operator or workshop manual. There is no safe universal setting.
Why does my track keep coming off?
Check track tension, idler and sprocket wear, debris build-up, damaged track components and operating technique.
Why is one side of my excavator travelling slower?
Possible causes include track binding, travel motor wear, final-drive problems, control-valve faults or hydraulic pump/flow problems.
How often should final-drive oil be changed?
Use the service interval for the exact model. Final drives contain relatively little oil, so neglect can become expensive quickly.
Can I dismantle a recoil spring myself?
Only with the correct workshop procedure and equipment. The spring stores extremely high energy and can cause severe injury.
Undercarriage wear is expensive but visible. Regular cleaning, correct track tension and early oil-leak checks can prevent much larger repair bills.