09-11-2025, 02:59 PM
The Legacy of IMT and Its Loader Variants
Iowa Mold Tooling Co., Inc. (IMT), founded in 1961, built its reputation manufacturing service truck cranes, tire handlers, and knuckleboom loaders. While most IMT units are associated with utility fleets and drywall delivery trucks, some were adapted for forestry use, particularly in the hardwood regions of the northeastern United States. These adaptations often involved retrofitting grapple arms onto knuckleboom loaders originally designed for palletized cargo.
The loader in question, mounted on a Ford L9000 chassis, appears to be one such IMT unit. With its twin-stick control, extendable boom, and fold-down outriggers, it reflects a hybrid design—part service crane, part log loader. The absence of decals and data plates complicates identification, but the mechanical layout and part numbers point toward IMT’s T30 or T50 series, which were occasionally repurposed for short log handling.
Terminology annotation:
- Knuckleboom loader: A hydraulic crane with multiple pivot points, allowing compact folding and extended reach.
- Outrigger: A stabilizing leg that extends from the chassis to prevent tipping during lifting operations.
Gear Shaft Failure and Rotor Drive Diagnosis
The immediate mechanical issue involves a destroyed gear or spline shaft responsible for rotating the main boom. This shaft is part of the rotor drive assembly, which may use a rack-and-pinion or planetary gear configuration depending on the model. IMT’s older loaders often used direct hydraulic rotation with mechanical reduction, making shaft replacement both critical and costly.
Repair steps:
- Spline shaft: A shaft with ridges that fit into matching grooves, transmitting torque without slippage.
- Planetary gear: A gear system with a central sun gear, orbiting planet gears, and an outer ring gear, used for torque multiplication.
Hydraulic Fluid Selection and System Flushing
The loader’s hydraulic system requires a complete fluid flush due to contamination and unknown service history. IMT manuals from the era recommend automatic transmission fluid (ATF), typically Type A or Dexron III, though modern practice favors AW 10 hydraulic oil for better thermal stability and wear protection.
Fluid selection considerations:
- AW hydraulic oil: Anti-wear hydraulic fluid formulated to protect pumps and valves under pressure.
- Suction screen: A mesh filter placed at the fluid intake to prevent large particles from entering the pump.
Operational Longevity and Preventative Maintenance
To extend the life of the loader and minimize downtime:
- Shock loading: Sudden application of force that exceeds design limits, often caused by abrupt joystick movements.
- Relief valve: A hydraulic valve that limits system pressure to prevent damage.
Field Adaptation and Historical Context
IMT loaders with grapples were more common in the hardwood regions of the Northeast and Midwest, where short logs and tight landings required compact, maneuverable equipment. Many units were mounted on Ford, International, or Kenworth chassis and operated by independent loggers or small mills. Over time, these machines were modified with homemade grapples, extended booms, and custom outriggers.
In one case, a logger in Maine retrofitted an IMT drywall crane with a Barko-style grapple and used it for over a decade in mixed hardwood stands. The loader’s compact footprint and twin-stick control made it ideal for selective cutting and roadside loading.
Suggestions:
- Selective cutting: A forestry method where only certain trees are harvested, preserving canopy and biodiversity.
- Retrofit: The process of modifying existing equipment with new components or capabilities.
Conclusion
Identifying and restoring an IMT log loader requires mechanical intuition, historical context, and a methodical approach to hydraulic and structural systems. While the original data plate may be missing, the loader’s design speaks to a legacy of adaptation and durability. With the right parts, fluid, and preventative care, this machine can return to productive service—lifting logs, turning rotors, and honoring the ingenuity of those who keep old iron alive.
Iowa Mold Tooling Co., Inc. (IMT), founded in 1961, built its reputation manufacturing service truck cranes, tire handlers, and knuckleboom loaders. While most IMT units are associated with utility fleets and drywall delivery trucks, some were adapted for forestry use, particularly in the hardwood regions of the northeastern United States. These adaptations often involved retrofitting grapple arms onto knuckleboom loaders originally designed for palletized cargo.
The loader in question, mounted on a Ford L9000 chassis, appears to be one such IMT unit. With its twin-stick control, extendable boom, and fold-down outriggers, it reflects a hybrid design—part service crane, part log loader. The absence of decals and data plates complicates identification, but the mechanical layout and part numbers point toward IMT’s T30 or T50 series, which were occasionally repurposed for short log handling.
Terminology annotation:
- Knuckleboom loader: A hydraulic crane with multiple pivot points, allowing compact folding and extended reach.
- Outrigger: A stabilizing leg that extends from the chassis to prevent tipping during lifting operations.
Gear Shaft Failure and Rotor Drive Diagnosis
The immediate mechanical issue involves a destroyed gear or spline shaft responsible for rotating the main boom. This shaft is part of the rotor drive assembly, which may use a rack-and-pinion or planetary gear configuration depending on the model. IMT’s older loaders often used direct hydraulic rotation with mechanical reduction, making shaft replacement both critical and costly.
Repair steps:
- Remove the damaged shaft and inspect mating surfaces for wear
- Identify part number via casting marks or cross-reference with IMT archives
- Measure spline count, diameter, and keyway dimensions for fabrication if OEM part is unavailable
- Replace associated bearings and seals to prevent premature failure
- Use induction-hardened steel for replacement shafts to improve longevity
- Apply anti-seize compound on spline interfaces during installation
- Torque fasteners to spec and recheck after 10 hours of operation
- Spline shaft: A shaft with ridges that fit into matching grooves, transmitting torque without slippage.
- Planetary gear: A gear system with a central sun gear, orbiting planet gears, and an outer ring gear, used for torque multiplication.
Hydraulic Fluid Selection and System Flushing
The loader’s hydraulic system requires a complete fluid flush due to contamination and unknown service history. IMT manuals from the era recommend automatic transmission fluid (ATF), typically Type A or Dexron III, though modern practice favors AW 10 hydraulic oil for better thermal stability and wear protection.
Fluid selection considerations:
- Operating temperature range: 20°F to 80°F (–6°C to 27°C)
- Pump type: Gear or vane pump (to be confirmed via inspection)
- Reservoir capacity: Estimate based on cylinder size and hose length
- Use AW 10 hydraulic oil for moderate climates and better anti-wear properties
- Flush system with low-viscosity flushing oil before refilling
- Replace all filters and inspect suction screens for debris
- Label reservoir with fluid type and change interval
- AW hydraulic oil: Anti-wear hydraulic fluid formulated to protect pumps and valves under pressure.
- Suction screen: A mesh filter placed at the fluid intake to prevent large particles from entering the pump.
Operational Longevity and Preventative Maintenance
To extend the life of the loader and minimize downtime:
- Grease all pivot points weekly, especially boom joints and grapple pins
- Inspect hoses for abrasion and replace any with bulges or cracks
- Test hydraulic pressure quarterly and adjust relief valves as needed
- Keep a logbook of service intervals, fluid changes, and part replacements
- Install quick-connect pressure test ports for easier diagnostics
- Use UV dye in hydraulic fluid to detect leaks under blacklight
- Train operators on smooth control input to reduce shock loading
- Shock loading: Sudden application of force that exceeds design limits, often caused by abrupt joystick movements.
- Relief valve: A hydraulic valve that limits system pressure to prevent damage.
Field Adaptation and Historical Context
IMT loaders with grapples were more common in the hardwood regions of the Northeast and Midwest, where short logs and tight landings required compact, maneuverable equipment. Many units were mounted on Ford, International, or Kenworth chassis and operated by independent loggers or small mills. Over time, these machines were modified with homemade grapples, extended booms, and custom outriggers.
In one case, a logger in Maine retrofitted an IMT drywall crane with a Barko-style grapple and used it for over a decade in mixed hardwood stands. The loader’s compact footprint and twin-stick control made it ideal for selective cutting and roadside loading.
Suggestions:
- Reinforce boom pivot welds if retrofitted with heavier grapples
- Install LED work lights for night loading and visibility
- Use rubber pads on outriggers to prevent road damage during deployment
- Selective cutting: A forestry method where only certain trees are harvested, preserving canopy and biodiversity.
- Retrofit: The process of modifying existing equipment with new components or capabilities.
Conclusion
Identifying and restoring an IMT log loader requires mechanical intuition, historical context, and a methodical approach to hydraulic and structural systems. While the original data plate may be missing, the loader’s design speaks to a legacy of adaptation and durability. With the right parts, fluid, and preventative care, this machine can return to productive service—lifting logs, turning rotors, and honoring the ingenuity of those who keep old iron alive.
