A telehandler combines the lifting ability of a forklift with a telescopic boom and construction-machine driveline. Safe operation depends on the boom structure, wear pads, chains or extension system, carriage, hydraulics, steering, stabilizers and the machine’s load-management system all working correctly.
Boom wear limits, chain adjustment, hydraulic pressures, load charts, stabilizer requirements and safety-system calibration are model-specific. Use the correct operator and workshop manual for the exact telehandler and serial range.
1. Main Telehandler Systems
A typical telehandler includes:
- Telescopic boom
- Boom lift cylinders
- Extension/retraction system
- Fork carriage
- Attachment tilt cylinder
- Hydraulic pump and control valve
- Four-wheel steering
- Transmission and axles
- Stabilizers on some models
- Load-management or stability system
2. Telescopic Boom
The boom may contain several sliding sections.
Movement is controlled by:
- Hydraulic cylinders
- Chains
- Cables
- Combination cylinder-and-chain systems
3. Boom Wear Pads
Wear pads support and guide the sliding boom sections.
Inspect For
- Excessive clearance
- Uneven wear
- Missing shims
- Damaged retaining hardware
- Dry or contaminated sliding surfaces
4. Symptoms of Worn Boom Pads
Possible signs include:
- Boom rattling
- Side movement
- Uneven extension
- Scoring of boom sections
- Difficulty retracting
Do not set wear-pad clearance by feel alone. Use the exact measurement and shim procedure in the workshop manual.
5. Boom Chains
Some telehandlers use chains to synchronize boom extension.
Check chains for:
- Elongation
- Corrosion
- Damaged links
- Uneven tension
- Lubrication condition
6. Chain Adjustment
Incorrect chain adjustment can cause:
- Uneven boom movement
- Boom sections not fully retracting
- Excessive chain load
- Structural damage
Use the model-specific setting procedure.
7. Boom Extension Cylinder
Possible faults include:
- External seal leakage
- Internal bypass
- Bent rod
- Damaged mountings
8. Boom Lift Cylinders
Lift-cylinder faults may cause:
- Boom drift
- Weak lifting
- Uneven movement
- External oil leakage
9. Load-Holding Valves
Telehandler cylinders commonly use load-holding or counterbalance valves to help prevent uncontrolled movement.
Problems may cause:
- Boom drift
- Jerky lowering
- Slow movement
- Failure to hold load
Use the manufacturer’s approved boom support or service procedure. A hydraulic hose or valve can fail without warning.
10. Fork Carriage
Inspect the carriage for:
- Cracks
- Bent fork bars
- Worn locking pins
- Loose bushes
- Damaged attachment locks
11. Fork Inspection
Check forks for:
- Cracks
- Bending
- Excessive heel wear
- Unequal height
- Damaged locking devices
Forks carry the full load and should not be casually repaired or modified.
12. Carriage Tilt
Carriage tilt may use one or more hydraulic cylinders.
Faults can include:
- Cylinder bypass
- Control-valve leakage
- Pivot wear
- Load-holding valve fault
13. Attachment Quick Couplers
Telehandlers may use mechanical or hydraulic attachment locks.
Check:
- Lock pins fully engaged
- Wear in hooks and pins
- Hydraulic lock pressure where applicable
- Correct attachment recognition on electronic systems
14. Hydraulic System
Telehandlers may use:
- Gear pumps
- Variable-displacement pumps
- Load-sensing systems
Hydraulics may power:
- Boom lift
- Boom extension
- Carriage tilt
- Stabilizers
- Auxiliary attachments
15. All Hydraulic Functions Weak
Possible causes include:
- Low oil level
- Blocked filter
- Pump wear
- Main relief valve fault
- Load-sense problem
- Engine not reaching rated speed
16. One Function Weak
If only one function is affected, check:
- Its cylinder
- Specific valve spool
- Port relief/counterbalance valve
- Related hoses and couplers
17. Hydraulic Overheating
Possible causes include:
- Valve held on relief
- Restricted cooler
- Internal leakage
- Wrong oil
- Load-sense fault
- Continuous auxiliary flow
18. Stabilizers / Outriggers
Some telehandlers use stabilizers to increase lifting capacity or stability.
Check:
- Cylinder leakage
- Pivot wear
- Pad condition
- Ground-contact sensors
- Lock/check valves
19. Stabilizer Interlocks
On some machines, available boom movement or lifting capacity changes depending on whether stabilizers are deployed.
Do not bypass these systems.
20. Load Charts
The load chart shows safe lifting capacity according to:
- Boom extension
- Boom angle
- Load weight
- Attachment fitted
- Stabilizer position where applicable
The chart is specific to the machine and attachment.
Capacity changes dramatically as the boom extends. Use only the chart supplied for the exact machine and approved attachment.
21. Load-Moment Indicator / Stability System
Modern telehandlers may use sensors for:
- Boom angle
- Boom extension
- Rear axle load
- Stabilizer position
- Attachment identification
The controller may warn or restrict movement as stability limits are approached.
22. Stability System Fault Codes
Possible causes include:
- Angle sensor fault
- Extension sensor fault
- Load sensor fault
- Wiring/connector problem
- Calibration required
Do not bypass a stability warning system.
23. Steering Modes
Telehandlers commonly offer:
- Front-wheel steering
- Four-wheel coordinated steering
- Crab steering
24. Steering Alignment
If wheels do not return to the correct alignment:
- Check steering mode sensors
- Check axle position sensors
- Check hydraulic cylinders
- Carry out calibration where specified
25. Axles and Hubs
Inspect:
- Axle oil
- Hub oil where separate
- Planetary reductions
- Steering joints
- Differential locks
- Brake performance
26. Transmission
Telehandlers may use:
- Torque-converter powershift
- Power shuttle
- Hydrostatic drive
Loss of drive may be hydraulic, electrical or mechanical.
27. Machine Will Not Drive
Check:
- Transmission oil level
- Parking brake release
- Neutral switch
- Seat/safety interlocks
- Transmission fault codes
- Clutch pressure
28. Boom Structure Inspection
Inspect regularly for:
- Cracks
- Distortion
- Damaged welds
- Scoring
- Loose wear-pad hardware
Structural defects should be assessed properly before continued lifting work.
29. Best Diagnostic Order
- Record fault codes and warning messages.
- Check hydraulic and transmission oil levels.
- Inspect boom, chains, wear pads and carriage.
- Check electrical interlocks and stability sensors.
- Check hydraulic pressure/flow where required.
- Check cylinder internal leakage.
- Calibrate sensors only using the correct procedure.
- Verify operation with no load before returning to service.
30. Telehandler Checklist
| Area | Check |
|---|---|
| Boom | No cracks, scoring or excessive play. |
| Wear pads | Clearance within specification. |
| Chains/cables | Condition and adjustment correct. |
| Carriage/forks | Secure, undamaged and locking correctly. |
| Hydraulics | No leaks, drift or weak functions. |
| Stabilizers | Hold securely and sensors work. |
| Steering | Modes and alignment correct. |
| Load system | Warnings and interlocks operational. |
| Manual data | Exact load chart and service values used. |
Related Agrimanual Manuals
Boom settings, hydraulic pressures, load-management systems and calibration procedures are telehandler-specific.
- Search Agrimanual telehandler workshop manuals
- Search Agrimanual JLG telehandler manuals
- Request a manual if your machine is not listed
Frequently Asked Questions
Why does my telehandler boom rattle when extending?
Check boom wear pads, shims, chain/cable adjustment and sliding-surface condition.
Why does the boom creep down?
Possible causes include cylinder internal leakage, control-valve leakage or a load-holding/counterbalance valve fault.
Can I bypass a load-moment or stability sensor?
No. These systems are safety-critical and should be diagnosed and repaired using the correct manual.
Why will the machine not drive even though the engine runs normally?
Check transmission oil, parking-brake release, interlocks, shuttle/gear selection, fault codes and clutch pressure.
Can I use a load chart from a similar telehandler?
No. Load charts are specific to the machine configuration and approved attachment.
On a telehandler, boom condition and safety systems matter as much as hydraulic power. Check structure, wear, sensors and load information before concentrating only on pressure and flow.