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Hitachi EX60URG Background and Market History
The Hitachi EX60URG is a compact hydraulic excavator originally manufactured for the Japanese domestic market. Built by Hitachi Construction Machinery, a company founded in 1970 and known for its precision engineering, the EX60URG was part of the EX series that dominated the 5–7 ton class in the 1990s. These machines were widely exported as used units to Australia, the UK, and Southeast Asia, often arriving with Japanese-language manuals and unique configurations. The EX60URG typically features an Isuzu diesel engine, a side-mounted boom, and a compact tail swing, making it ideal for urban excavation and utility work.
Terminology Note
When disassembling the slew gearbox, one common question is whether the planetary gears require timing during reassembly. In the case of the EX60URG, no timing marks or alignment procedures are necessary. The planetary gears operate in a continuous mesh configuration, driven by hydraulic pressure and gear oil lubrication. Unlike final drive gearboxes, which may require timing for differential balance, the slew gearbox functions purely on torque transfer and does not rely on synchronized gear phasing.
Lubrication Strategy for the Slew Ring Gear
The EX60URG features three grease points for the slew ring bearings and one for the internal ring gear. The internal gear is not submerged in oil but instead relies on periodic manual greasing. The access point is typically located beneath a small cover plate between the rotary joint and boom lift cylinder. Grease should be applied directly to the gear teeth at multiple points to ensure even distribution.
Gearbox Oil and Drainage Confusion
A notable issue arises when users discover a hose connected to the bottom of the slew gearbox, leading to the hydraulic return manifold. This configuration is not standard and likely stems from aftermarket modifications or auction repairs. The correct setup involves a drain plug and fill port, with the gearbox filled with 2.3 liters of 90W gear oil. Hydraulic oil should never mix with gear oil, as it compromises lubrication and can lead to seal failure.
In one case, a user mistakenly filled the gearbox with over 10 liters of oil, unaware that the dipstick was not registering due to a missing retaining ring and damaged seal. The excess oil leaked into the slew ring chamber, causing external seal failure and prompting a full teardown.
Seal Failure and Motor Leakage
If the motor shaft seal fails, hydraulic oil can leak into the gearbox, overfilling it and eventually blowing the gearbox shaft seal. This failure mode is common in older machines and requires attention to:
Field Repair Tips and Lessons Learned
Rebuilding the slew motor and gearbox on a Hitachi EX60URG requires mechanical precision, attention to lubrication systems, and awareness of aftermarket modifications. By restoring proper seals, removing non-standard return lines, and using correct gear oil, operators can ensure smooth rotation and long-term reliability. The EX60URG, despite its compact size, remains a capable and serviceable machine when maintained with care and technical insight.
The Hitachi EX60URG is a compact hydraulic excavator originally manufactured for the Japanese domestic market. Built by Hitachi Construction Machinery, a company founded in 1970 and known for its precision engineering, the EX60URG was part of the EX series that dominated the 5–7 ton class in the 1990s. These machines were widely exported as used units to Australia, the UK, and Southeast Asia, often arriving with Japanese-language manuals and unique configurations. The EX60URG typically features an Isuzu diesel engine, a side-mounted boom, and a compact tail swing, making it ideal for urban excavation and utility work.
Terminology Note
- Slew Motor: A hydraulic motor that powers the rotation of the upper structure of an excavator.
- Slew Ring Gear: A large gear mounted to the undercarriage that interfaces with the slew motor’s pinion gear.
- Reduction Gearbox: A gear assembly that reduces motor speed and increases torque for controlled rotation.
When disassembling the slew gearbox, one common question is whether the planetary gears require timing during reassembly. In the case of the EX60URG, no timing marks or alignment procedures are necessary. The planetary gears operate in a continuous mesh configuration, driven by hydraulic pressure and gear oil lubrication. Unlike final drive gearboxes, which may require timing for differential balance, the slew gearbox functions purely on torque transfer and does not rely on synchronized gear phasing.
Lubrication Strategy for the Slew Ring Gear
The EX60URG features three grease points for the slew ring bearings and one for the internal ring gear. The internal gear is not submerged in oil but instead relies on periodic manual greasing. The access point is typically located beneath a small cover plate between the rotary joint and boom lift cylinder. Grease should be applied directly to the gear teeth at multiple points to ensure even distribution.
Gearbox Oil and Drainage Confusion
A notable issue arises when users discover a hose connected to the bottom of the slew gearbox, leading to the hydraulic return manifold. This configuration is not standard and likely stems from aftermarket modifications or auction repairs. The correct setup involves a drain plug and fill port, with the gearbox filled with 2.3 liters of 90W gear oil. Hydraulic oil should never mix with gear oil, as it compromises lubrication and can lead to seal failure.
In one case, a user mistakenly filled the gearbox with over 10 liters of oil, unaware that the dipstick was not registering due to a missing retaining ring and damaged seal. The excess oil leaked into the slew ring chamber, causing external seal failure and prompting a full teardown.
Seal Failure and Motor Leakage
If the motor shaft seal fails, hydraulic oil can leak into the gearbox, overfilling it and eventually blowing the gearbox shaft seal. This failure mode is common in older machines and requires attention to:
- Shaft seal integrity
- Bearing condition
- Seal sleeve wear
- Retaining ring placement
Field Repair Tips and Lessons Learned
- Fill the gearbox with oil before reinstalling the slew motor to avoid slow fill rates through narrow pipes.
- Use a dipstick to monitor oil level after one hour of operation to detect hydraulic contamination.
- Always verify parts diagrams against actual machine configuration, especially with Japanese imports.
- Avoid assuming factory paint indicates original configuration—many auction machines are repainted.
Rebuilding the slew motor and gearbox on a Hitachi EX60URG requires mechanical precision, attention to lubrication systems, and awareness of aftermarket modifications. By restoring proper seals, removing non-standard return lines, and using correct gear oil, operators can ensure smooth rotation and long-term reliability. The EX60URG, despite its compact size, remains a capable and serviceable machine when maintained with care and technical insight.
