Unusual Noises from Electric Pallet Stacker: Causes & Solutions

In the daily operation of an Electric Pallet Stacker, abnormal noise is often the first signal that the equipment is "hurting." Unlike a complete failure to start, it does not immediately interrupt operations—but it may be an early sign of bearing corrosion, dry chain friction, or gear pump wear. Taking Diding Lift's 2T Electric Walkie Pallet Stacker CDDA as an example, its AC motors, Bucher hydraulic system, and maintenance-free gel battery reduce the probability of noise-related faults at the design level. However, under long-term high-frequency operation, the travel wheel assemblies, mast chains, and hydraulic pump station remain high-risk areas for abnormal noise. This guide categorizes noise by source location, outlining causes and handling paths to help you intervene before the fault escalates.

1. Travel and Wheel Assembly Noise: Jamming, Metal Friction, and Periodic Sounds

1.1 Debris Wrapped Around Legs (Straddle-Specific Issue)

As a straddle stacker, the CDDA20's leg area has low ground clearance and easily wraps packaging straps, plastic ropes, or tape. When these debris items jam into the load wheels, pushing and pulling feel noticeably jammed, accompanied by irregular friction sounds. Handling: Stop the machine immediately and clear wrapped material from the legs and load wheels. If left uncleared, wrapped debris forces uneven wheel wear and eventually damages bearings.

1.2 Wheel Bearing Wear or Corrosion

Drive wheel and load wheel bearings are prone to corrosion in humid environments or after high-pressure washing. Corroded bearings produce a continuous "swishing" or metal friction sound when rotating, with noticeably increased pushing resistance. Judgment method: Lift the equipment so wheels are off the ground and rotate wheels manually, feeling for jamming or wobble. If rotation is unsmooth or wobble is obvious, replace the bearings. In routine maintenance, wheel bearings should receive periodic grease application—not wait until noise appears.

1.3 Loose Tire Bolts and Leg Deformation

Loose tire fixing bolts produce a periodic "clunk" that varies with speed, accompanied by slight body wobble. If a leg has been struck and deformed, it disrupts wheel parallelism, causing uneven tire wear and continuous friction noise. Handling: Tighten tire bolts in a diagonal sequence; check legs for impact marks, correcting or replacing deformed components.

2. Mast and Chain Noise: "Squeaking" and "Clicking" During Lifting

2.1 Insufficient Chain Lubrication and Elongation

When mast lifting chains run dry, they produce a sharp "squeaking" sound, most noticeable during mid-to-high lifting. If chains remain unlubricated for extended periods, link wear accelerates chain elongation, producing a "clicking" jump-tooth sound during lifting—and in severe cases, the chain may derail from the sprocket. Handling: Clean dust from the chain surface, then apply dedicated chain lubricating grease evenly. Check chain sag; if significantly elongated and cannot be adjusted via the tensioning device, replace the chain.

2.2 Abnormal Mast Rail and Roller Clearance

Excessive or insufficient clearance between mast rails and rollers produces abnormal noise during lifting. When clearance is too large, forks wobble and produce impact sounds during lifting; when too tight, rollers and rails rub, producing continuous friction noise. Handling: Check rail surfaces for debris or scratches, and adjust roller clearance to standard values.

2.3 Loose Fork-to-Carriage Connection

When the clearance between fork upper/lower pins and the carriage crossbeam is excessive, metal impact sounds occur during travel or lifting. Handling: Check pin wear, replacing pins or adjusting clearance as needed.

3. Hydraulic System Noise: "Humming" and "Hissing" from the Pump Station

3.1 Insufficient Oil or Clogged Filter (Cavitation Noise)

When oil level is low or the suction filter is clogged, the pump draws in air, producing a deep "humming" or "gurgling" sound along with weak lifting. This is the most common and easily resolved type of hydraulic noise. Handling: Top up with the specified hydraulic oil; clean or replace the suction filter. Note: Do not repeatedly start the pump station in a low-oil condition—this can cause permanent pump damage.

3.2 Emulsified Oil (Water Ingress)

When hydraulic oil turns milky white due to emulsification, the pump produces an irregular "hissing" sound and system pressure becomes unstable. Emulsified oil has significantly reduced lubricity, accelerating pump and cylinder wear. Handling: Completely replace the hydraulic oil and check cylinder seals for damage that may have allowed moisture ingress.

3.3 Gear Pump Wear or Coupling Issues

After internal gear wear in the gear pump, a continuous metal friction sound is produced during operation, and pressure build-up becomes difficult. When the coupling rubber pad breaks, the motor turns but the pump does not rotate or rotates unevenly, producing an intermittent "clicking" sound. Handling: Replace the gear pump if worn; replace the coupling pad if broken and check pump-to-motor alignment.

4. Motor and Brake Noise: "Whining" and "Friction" in the Drive Area

4.1 Motor Bearing Wear

After bearing wear in the drive or lift motor, a high-frequency "whining" or "swishing" sound is produced during operation, intensifying with speed. Although the CDDA20's AC motors require no carbon brush replacement, bearing lubrication and replacement remain maintenance items in long-term use. Handling: After power-off, manually rotate the motor shaft (if accessible) to feel for jamming; replace bearings if worn.

4.2 Electromagnetic Brake Drag

When brake clearance is improperly adjusted or the spring is fatigued, the brake pad and disc make slight contact in the non-braking state, producing continuous friction noise during travel, with increased motor load and faster battery drain. Handling: Adjust brake clearance; replace the brake pad if wear exceeds limits.

5. Safety Principles and Priority for Noise Troubleshooting

5.1 Locate the Sound Source Before Disassembly

The first step in noise troubleshooting is not disassembly, but using hearing to locate the source area: does it occur during travel or lifting? Front or rear? Low-frequency dull sound or high-frequency sharp sound? This significantly narrows the troubleshooting scope. Industry experience recommends following the principle of "electrical before mechanical, simple before complex".

5.2 Stop Use Immediately If Noise Is Accompanied By:

• Brake failure or noticeably reduced braking force

• Visible deformation of mast or legs

• Significant hydraulic oil leakage

• Motor smoke or odor

• Chain jumping or derailing from sprocket

6. Conclusion and Action Recommendations

Abnormal noise from an Electric Pallet Stacker is essentially an early signal of component wear or lubrication failure. Troubleshoot by source category: travel noise prioritizes leg debris and wheel bearings; lifting noise prioritizes chain lubrication and rail clearance; hydraulic noise prioritizes oil level and filter. Most noises can be eliminated after cleaning, lubrication, or small-part replacement—major overhaul is usually unnecessary.

Diding Lift has 12 years of experience and a 65,000 m² factory & workshop, with products complying with EN 12895:2015 and EN ISO 3691-1:2015 European standards, certified to ISO 9001:2015 quality management system and CE safety certification, and supports ODM/OEM cooperation & customization. Its 2T Electric Walkie Pallet Stacker CDDA, with its AC motors, Bucher hydraulic system, and maintenance-free gel battery, reduces the probability of noise-related faults and provides complete after-sales technical support.

For the CDDA20 noise troubleshooting checklist or diagnostic guidance for specific sound sources, please send an email to sales@didinglift.com, and our professional team will provide one-on-one support.

References

1. Xin Niu Dun Forklift. (2026). Walkie Straddle Electric Pallet Stacker On-Site Troubleshooting and Maintenance Plan.

2. Zhihu. (2022). Electric Forklift Repair Troubleshooting and Maintenance Methods.

3. Xin Niu Dun Forklift. (2026). Three Key Maintenance Points to Extend Walkie Electric Stacker Service Life.

4. HC X Series Maintenance Manual. Troubleshooting – Excessive System Noise.

5. Qingdao Best Electric Forklift. (2026). Electric Forklift Common Fault Diagnosis and Maintenance Plan.