XCMG XE35U Hydraulic Thumb Setup and Pin Conversion Challenges

[MikePhua]

XCMG’s Rise and the XE35U Mini Excavator
XCMG, founded in 1943 in Xuzhou, China, has grown into one of the world’s largest construction equipment manufacturers. With a strong presence in over 180 countries, the company has focused heavily on compact equipment in recent years. The XE35U mini excavator, introduced in the early 2020s, is part of XCMG’s push into the global compact excavator market. Designed for urban construction, landscaping, and utility work, the XE35U is a 4-ton class zero-tail swing machine that balances power, maneuverability, and affordability.
Sales of the XE35U have surged in Southeast Asia, Eastern Europe, and Latin America, where contractors seek reliable alternatives to Japanese and Korean brands. Its compact footprint and Tier 4 Final compliance make it suitable for both regulated and emerging markets.
Auxiliary Hydraulics and Thumb Compatibility
The XE35U comes standard with a single-direction auxiliary hydraulic circuit, typically used for attachments like hydraulic breakers or thumbs. However, the factory configuration often lacks a return line or proportional control, limiting its compatibility with two-way hydraulic thumbs.
Key terminology includes:

• Auxiliary Hydraulic Circuit: A secondary hydraulic line used to power attachments beyond the main boom and arm.
  
• Hydraulic Thumb: A pivoting clamp mounted opposite the bucket, used for grabbing debris, rocks, or logs.
  
• One-Way Flow: Hydraulic fluid flows in one direction only, suitable for impact tools but not for bi-directional actuators.
  
• Two-Way Flow: Allows fluid to reverse direction, essential for thumbs that open and close hydraulically.
  

To install a hydraulic thumb on the XE35U, operators must:

• Add a return line to the tank or valve block.
  
• Install a diverter valve or proportional joystick switch.
  
• Confirm flow rate and pressure compatibility (typically 30–50 L/min at 180–210 bar for mini excavators).
  

In one case, a contractor in Malaysia retrofitted his XE35U with a two-way thumb using a solenoid diverter and foot pedal control. The modification cost under $800 and took two days to install, dramatically improving material handling efficiency.
Pin and Bushing Conversion Considerations
The XE35U’s bucket linkage uses 35mm diameter pins with a stick gap of 144mm and a center-to-center (C-to-C) spacing of 195mm. These dimensions are critical for quick hitch compatibility. However, many aftermarket quick hitches are designed for 40mm pins, creating a mismatch.
Terminology notes:

• Pin Diameter: The thickness of the steel pin connecting bucket or attachment to the stick.
  
• Stick Gap: The internal width between the mounting ears on the excavator stick.
  
• C-to-C Spacing: The distance between the centers of the upper and lower mounting holes.
  

Operators facing compatibility issues have two options:

• Custom Quick Hitch Fabrication
  Build a hitch tailored to 35mm pins and 144mm gap. Requires precision machining and welding. Ideal for remote regions or unique attachment setups.
  
• Pin and Bushing Upgrade
  Convert the stick and bucket to accept 40mm pins by replacing bushings and possibly boring out the ears. This method improves compatibility with standard hitches but may weaken structural integrity if not done properly.
  

A technician in Queensland attempted a conversion but found that the stick ears were too thin to safely bore out. Instead, he opted for a custom hitch with hardened 35mm pins and reinforced side plates.
Maintenance and Wear Management
Pin and bushing wear is inevitable in excavators, especially when using heavy attachments or operating in abrasive conditions. Recommendations include:

• Grease Daily
  Use high-pressure grease with molybdenum disulfide to reduce friction.
  
• Inspect Monthly
  Check for oval wear, pin movement, and bushing cracks. Replace components showing more than 1mm of wear.
  
• Use Hardened Pins
  Upgrade to induction-hardened pins for longer life in high-cycle applications.
  
• Install Wear Shims
  Add shims between ears and attachments to reduce side play and prevent hammering.
  

In 2022, a rental fleet in Brazil reported a 30% reduction in downtime after switching to hardened pins and implementing a strict greasing schedule. The improvement was most noticeable in machines used for demolition and forestry work.
Operator Feedback and Field Adaptations
Operators appreciate the XE35U’s smooth hydraulics and responsive controls but often cite limitations in attachment compatibility. One user in Poland fabricated a manual quick hitch using 35mm pins and a locking wedge, allowing fast bucket swaps without hydraulic actuation.
Another operator in Thailand added a hydraulic thumb using a joystick-mounted switch and a flow divider. The setup allowed simultaneous boom and thumb movement, improving productivity in bamboo clearing operations.
Conclusion
The XCMG XE35U is a capable mini excavator with strong core features, but its auxiliary hydraulics and pin dimensions require careful planning when adding attachments. Whether upgrading to a hydraulic thumb or adapting quick hitches, understanding the machine’s geometry and flow characteristics is essential. With thoughtful modifications and proactive maintenance, the XE35U can match the versatility of more established brands while offering cost advantages and global support.