Grove TM120T Truck Crane Field Performance and Mechanical Insights

[MikePhua]

The TM120T and Grove’s Engineering Legacy
The Grove TM120T is a truck-mounted hydraulic crane developed by Grove Manufacturing Company, a Pennsylvania-based firm founded in 1947 and later acquired by Manitowoc. Grove became a global leader in mobile crane technology by the 1980s, known for its telescoping booms, load moment indicators, and robust carrier platforms. The TM120T was designed for utility work, infrastructure maintenance, and light industrial lifting, offering a balance between highway mobility and jobsite capability.
With a rated lifting capacity of 120,000 pounds and a boom length exceeding 100 feet with extensions, the TM120T filled a niche between rough-terrain cranes and full-size all-terrain units. Its popularity peaked in the late 1990s, with hundreds of units deployed across North America and the Middle East.
Carrier and Chassis Configuration
The TM120T is built on a multi-axle truck chassis, often customized for regional transport laws. The carrier includes:

• Tandem rear axles with air suspension
  
• Hydraulic outriggers with automatic leveling
  
• Diesel engine (typically Cummins or Detroit) for road travel
  
• Secondary PTO-driven hydraulic pump for crane operation
  

Operators appreciated the ability to drive the crane to remote sites without a trailer, reducing mobilization costs. In one example from Nevada, a utility contractor used the TM120T to install transmission poles in mountainous terrain where larger cranes couldn’t navigate.
Boom Design and Load Handling
The TM120T features a four-section telescoping boom constructed from high-tensile steel. The boom extends hydraulically and includes:

• Internal wear pads and cable routing
  
• Boom angle sensor for load chart integration
  
• Manual or hydraulic jib extension for added reach
  

Key lifting specs:

• Main boom: ~35 to 105 feet
  
• Jib extension: ~30 feet
  
• Max tip height: ~140 feet
  
• Max radius: ~110 feet
  
• Rated capacity: 60 tons (varies by configuration)
  

The boom’s hydraulic sequencing allows smooth extension under load, though older units may suffer from cylinder drift or pad wear. Regular inspection of boom rollers and cable sheaves is essential to maintain lifting precision.
Hydraulic System and Control Layout
The crane’s hydraulic system includes:

• Tandem gear pumps or piston pumps
  
• Load-sensing valves
  
• Pilot-operated control levers
  
• Pressure relief circuits and accumulator tanks
  

Operators control the crane from a side-mounted cab with full visibility of the boom and load. The cab includes:

• Joystick or lever controls for boom, swing, and winch
  
• Load Moment Indicator (LMI) with override capability
  
• Emergency stop and anti-two-block system
  
• Heater and ventilation for cold-weather operation
  

In one case from Saskatchewan, a TM120T was used for bridge girder placement during winter. The operator noted that the cab heater was underpowered, prompting a retrofit with an auxiliary diesel heater to maintain visibility and comfort.
Electrical and Diagnostic Systems
Older TM120T units use analog gauges and basic wiring harnesses. Common electrical components include:

• Boom angle sensor
  
• Anti-two-block switch
  
• PTO engagement relay
  
• Outrigger position sensors
  

Failures often occur at connector junctions exposed to weather. Technicians recommend:

• Replacing corroded connectors with sealed Deutsch plugs
  
• Installing LED work lights with independent fusing
  
• Upgrading LMI systems to digital displays for better fault tracking
  

In one fleet in Texas, a TM120T experienced intermittent boom angle readings. The issue was traced to a cracked sensor housing. Replacing the sensor and resealing the harness resolved the fault.
Maintenance Strategy and Wear Points
Routine maintenance is critical for long-term reliability:

• Hydraulic fluid: Replace every 1000 hours or annually
  
• Boom pads: Inspect every 250 hours
  
• Winch cable: Replace every 2000 hours or when frayed
  
• Outrigger seals: Inspect quarterly
  
• Carrier engine: Follow OEM service intervals
  

Wear points include:

• Boom extension cylinders
  
• Swing gear teeth and bearings
  
• Winch drum bushings
  
• Outrigger pivot pins
  

In one case from Ohio, a TM120T developed swing hesitation. The cause was hardened grease in the swing bearing race. Flushing the race and switching to low-temperature grease restored smooth rotation.
Operator Stories and Field Wisdom
In Florida, a marine contractor used a TM120T to lift boat engines from docks. After 10 years of service, the boom began to chatter during extension. The crew replaced the wear pads and adjusted the hydraulic sequencing, restoring full performance.
In Arizona, a mining company deployed a TM120T for conveyor installation. The crane’s compact footprint and long boom reach allowed it to work between structures without repositioning. The operator praised its stability and ease of setup.
Conclusion
The Grove TM120T remains a versatile and dependable truck-mounted crane for mid-range lifting tasks. With proper maintenance, hydraulic care, and electrical upgrades, these machines continue to serve in utility, construction, and industrial roles. Whether lifting transformers in the Rockies or placing HVAC units in urban zones, the TM120T proves that smart design and mechanical resilience never go out of style.