Heavy Equipment Parts Glossary

A

Adapter: A connector or spacer that changes size or interface between components. Shop Adapters.

Aftermarket: A non-OEM replacement part that meets or exceeds factory specifications.

Alternator: A belt-driven electrical generator that converts mechanical energy into electricity to charge the battery and power electrical systems. Shop Alternators.

Arm: The excavator component that connects the boom to the bucket, providing digging reach and control. Also referred to as a stick, dipper, or crowd in various parts books and regions. Shop Excavator Arms.

Axle: A shaft assembly that carries wheel ends and supports differentials.

Axle Corners: Also known as Planetary Axle Wheel Ends, Final Drives, Planetary Gear Assembly, Axle Hub, Planetary Hub, or Wheel Hub. See Planetary Axle Wheel Ends.

Axle Housing: The outer casing that encloses and supports the axle shafts, gears, and differential, protecting them from dirt and damage while maintaining alignment.

Axle Shaft: A rotating steel shaft that transmits torque from the differential or planetary gear assembly to the wheels. Shop Axle Shafts.

B

Bellcrank: A pivoting lever that redirects or multiplies mechanical force within linkage systems such as steering, lift, or bucket controls. Shop Bellcranks.

Blade: A large steel cutting or grading plate used on dozers, graders, or scrapers to push or level material. Shop Blades.

Bogie Wheels: Load-bearing wheels used on compact track loaders (CTLs) and multi-terrain loaders (MTLs) that support and guide the rubber track along the undercarriage.

Boom: The main lifting arm on an excavator, crane, or similar machine. Often paired with an arm for digging reach. Shop Booms.

Bucket: A primary digging or loading attachment designed to scoop and move material. Available in multiple shapes for excavators, loaders, and backhoes. Shop Bucketss.

Bucket Teeth: Replaceable wear tips mounted on the edge of a bucket to penetrate material and protect the bucket lip. Shop Bucket Teeth.

C

C Frame: The main front frame assembly of a bulldozer that connects the blade to the push arms and tilt cylinders. Shop C Frames.

Cab & ROPS: The operator enclosure (cab) with a Roll Over Protective Structure designed to protect the operator in case of rollover or impact.

Camshaft: A rotating shaft inside a diesel engine that opens and closes the intake and exhaust valves in synchronization with the crankshaft.

Canopy: An open protective structure that shields the operator from sun and debris while maintaining visibility.

Counterweight: A heavy cast or fabricated component mounted on the rear of a machine to balance lifting loads and stabilize operation. Learn more about Counterweights.

Coupler: A quick-connect linkage system that attaches buckets or work tools to the machine. Designed for fast attachment changes without removing pins, available in both hydraulic and mechanical types.

Crank Case: The lower section of an engine block that houses the crankshaft and acts as an oil reservoir.

Crankshaft: The main rotating shaft in a diesel engine that converts the linear motion of pistons into rotational power.

Crowd: See Arm.

Cylinder Block: The main engine housing that contains the cylinders, coolant passages, and internal mounting points for major components.

Cylinder Head: The upper engine component that seals the combustion chamber and contains valves, injectors, and ports. Learn more about Cylinder Heads.

Cylinder Rod: A steel rod that transfers the motion of the piston to external mechanical systems in a hydraulic or engine cylinder.

D

Diesel Engine Rebuild Kit: A complete set of replacement internal components such as pistons, rings, gaskets, and bearings for engine overhaul. Learn more about Diesel Engine Rebuild Kits

Diesel Fuel Injectors & Pumps: Precision components that deliver pressurized diesel fuel into the combustion chamber at the correct timing and volume. Learn more about Diesel Fuel Injectors.

Differential: A drivetrain component that allows wheels to rotate at different speeds. Works with a Planetary gear set to distribute torque efficiently. Learn more about Differentials.

Dipper: See Arm.

Dipstick: A metal rod used to measure engine or hydraulic fluid levels.

Dump Box: The main load-carrying bed of an articulated dump truck that tilts to unload material.

E

Economy Valve: A flow-control valve that regulates hydraulic output for fuel efficiency.

ECU: The electronic control unit that manages engine or system performance.

Equalizer Bar: A pivoting bar that balances the left and right track frames on a bulldozer.

Exhaust Manifold: A cast or fabricated component that collects exhaust gases from engine cylinders and directs them to the turbocharger or exhaust pipe.

F

Final Drive: The planetary gear hub that transfers torque from the travel motor to the track sprocket on crawler machines such as excavators and mini excavators. The term is also used to describe the complete drive assembly, which includes both the travel motor and the planetary gear reduction unit. Shop Final Drives.

Filter: A component that removes contaminants from air, oil, fuel, or hydraulic fluid. Shop Filters.

Forks: Lifting tines mounted to a carriage or attachment for moving pallets, materials, or logs. Common on loaders, telehandlers, and forklifts.

Frame: The main structural foundation of a machine supporting all major components. Shop Frames.

Front & Rear Covers: Engine end housings that enclose timing gears, seals, and crankshaft ends to retain oil and protect internal components.

G

Grapple: A claw-like hydraulic attachment used for grabbing, sorting, and loading logs, scrap, or debris.

Grease Fitting: A small nozzle used to apply lubricant to moving parts.

Ground Engaging Tools (GET): Replaceable wear parts like teeth, edges, and shrouds that contact the ground.

Grouser Pads: Shop Steel Track Pads.

H

H Link: The H-shaped attachment connecting link between the bucket and stick that provides pivoting movement and load transfer. Shop H Links.

Hydraulic Breaker: A percussion attachment powered by hydraulic flow, used to break concrete, rock, or asphalt. Also called a hammer.

Hydraulic Control Valve: A directional valve that manages the flow of hydraulic oil to cylinders or motors, controlling movement and speed of machine functions such as boom, stick, and bucket. Learn more about Hydraulic Control Valves.

Hydraulic Cylinder: A linear actuator that provides movement for boom, stick, or lift systems. Shop Hydraulic Cylinders.

Hydraulic Oil Cooler: A heat exchanger that removes excess heat from hydraulic fluid to maintain proper system temperature and performance. Also known as an oil cooler. Learn more about Hydraulic Oil Coolers.

Hydraulic Pump: A unit that converts mechanical energy into hydraulic pressure and flow. Shop Hydraulic Pumps.

I

Idler: A wheel that guides and maintains track tension on a crawler machine. Shop Idlers.

J

Joystick: A hand lever that controls hydraulic functions or travel direction.

L

Linkage: A system of connecting arms and pins that controls bucket or attachment movement. Learn more about Linkage Components.

Log Arch: A curved steel frame attachment used for lifting and skidding logs in forestry operations.

Long Reach Boom-Arm: An extended boom and arm combination providing greater digging depth and reach for dredging or slope work. Learn more about Long Reach Boom Packages.

Luffing Cylinder: A hydraulic cylinder used to raise and lower a crane boom.

M

Meatball: Also known as a pumpkin and a differential. See Differential.

O

OEM: The original equipment manufacturer that builds factory parts for machines.

Oil Pump & Pan: The oil pump circulates lubrication throughout the engine, while the pan serves as the reservoir for stored oil.

O-Ring: A circular rubber seal that prevents leaks between connected components. Shop O Rings.

Operator Station: The area where machine controls, seat, and monitoring systems are located.

P

Pin: A hardened steel shaft used to connect joints in linkages or cylinders. Shop Pins.

Pilot Control: A low-pressure hydraulic system that signals main control valves.

Piston: A cylindrical component that moves up and down inside a diesel engine cylinder to compress air and transfer combustion force to the crankshaft. Shop Pistons.

Planetary: A gear reduction system used in final drives and differentials. Works with a differential to manage torque distribution. Shop Planetary Gear Reduction Systems.

Planetary Axle Wheel Ends: Gear assemblies located at the ends of drive axles that reduce speed and increase torque to the wheels on wheel loaders and articulated dump trucks. Also known as a planetary gear assembly, wheel end corners, axle hub, planetary hub, or wheel hub. Learn more about Planetary Axle Wheel Ends.

Pins & Bushings: Precision steel components forming pivot joints in equipment linkages, providing controlled motion and wear resistance. Learn more about Pins & Bushings.

Pump Drive: A gearbox connecting the engine to the hydraulic pump.

Pumpkin: Also known as a meatball and a differential. See Differential.

Q

Quick Coupler: A hydraulic or mechanical coupler that enables fast changeover of buckets or attachments on an excavator or a mini excavator. Learn more about Quick Couplers.

R

Radiator: A heat exchanger that cools engine coolant before it recirculates. Shop Radiators.

Rake: A multi-tine attachment designed to clear roots, debris, and brush from soil while leaving finer material behind. Shop Rakes.

Relief Valve: A hydraulic valve that limits system pressure to prevent damage.

Ring and Pinion: A matched gear set inside the differential that transfers rotational power from the driveshaft to the axle shafts, providing final gear reduction and direction change to the wheels.

Ripper: A heavy tooth-style attachment used to loosen hard ground, rock, or asphalt on a bulldozer. Shop Rippers.

Roller, Bottom: A lower track roller that supports the track chain’s weight.

Rubber Tracks: Continuous rubber belts that replace steel tracks on compact machines, providing smoother operation, lower ground pressure, and reduced vibration. Shop Rubber Tracks.

Rubber Track Pads: Replaceable pads that cover steel track shoes to protect paved surfaces and reduce noise. Available in bolt-on and clip-on styles. Learn more about Rubber Track Pads.

S

Seal Kit: A set of seals used to rebuild hydraulic components such as cylinders or pumps. Shop Seal Kits.

Shims: Thin metal spacers used for alignment or preload adjustments. Shop Shimss.

Slew Ring: A large bearing that allows the upper structure of an excavator to rotate on the undercarriage. Works with the swing motor to enable full rotation.

Starter Motor: An electric motor that cranks the engine during startup by engaging with the flywheel. Shop Starter Motors.

Steel Track Pads: Steel shoes bolted to the track chain that provide traction and durability on rough terrain. Also commonly referred to as grouser pads, steel track shoes, track pads. Shop Steel Track Pads.

Stick: See Arm.

Sprocket: A toothed wheel that drives the track chain. Shop Sprockets.

Sweeper: A rotating brush attachment for skid steers or loaders used to clear dust, dirt, and debris from pavement or job sites.

Swing Drive: The complete assembly that provides rotation to the upper structure of an excavator, consisting of the swing motor, swing gearbox, and swing bearing. Shop Swing Drives.

Swing Gear: The large ring gear within the swing drive system that transfers torque from the swing motor to rotate the upper structure of the excavator. Shop Swing Gears.

Swing Motor: A hydraulic motor that powers rotation of the upper structure of an excavator by driving the Slew Ring through a gear reduction system.

T

Tailgate: The hinged rear gate on an articulated dump truck dump body that opens to discharge material. Learn more about Tailgates.

Telehandler: A telescopic handler equipped with a boom and fork attachment for lifting materials.

Thumb: A hydraulic or mechanical clamp attached to a bucket for grabbing materials on an excavator. Shop Thumbs.

Torque Converter: A fluid coupling that transmits engine power to the transmission. Shop Torque Converters.

Track Adjuster: A spring-loaded assembly that maintains proper track tension. Shop Track Adjusters.

Track Chain: The series of links and bushings that form a crawler machine’s track.

Track Pads: Also commonly referred to as grouser pads, steel track shoes, or steel track pads. Shop Steel Track Pads.

Travel Alarm: An audible alarm that warns bystanders when the machine moves in reverse.

Travel Motor: The hydraulic motor that provides power to move a crawler machine. It mounts directly to the Final Drive housing to create the complete drive system.

Truck Bed: The load-carrying platform of a truck or hauler used for transporting materials.

Turbocharger: A forced induction device used on a diesel engine to increase power by using exhaust gases to spin a turbine and compress incoming air. Shop Turbochargers.

U

Undercarriage: The complete track system including rollers, idlers, sprockets, chains, track adjusters, and final drives. Shop Undercarriage Parts.

V

Valve Bank: A group of hydraulic control valves arranged together in one assembly.

Valve Cover: A metal or composite cover that seals the top of the cylinder head and prevents oil leakage around the valve train.

W

Water Pump: A mechanical pump that circulates coolant through the engine and radiator to regulate operating temperature. Shop Water Pumps.

Wear Plate: A replaceable plate that protects a structure from abrasion or impact.

Wheel End Corners: Also known as Planetary Axle Wheel Ends, Final Drives, Planetary Gear Assembly, Axle Hub, Planetary Hub, or Wheel Hub. See Planetary Axle Wheel Ends.

Winch: A rotating drum powered by hydraulic or electric drive used for pulling, lifting, or securing loads with cable or rope.

Y

Yoke: A connection component linking a driveshaft or pin assembly. Shop Yokes.

Z

Z-Bar Linkage: A loader linkage design used on wheel loaders that improves breakout force and lifting efficiency.

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