Product Overview
The 74318-DAH is a standard configuration model within the Danfoss 74318 Series of medium-duty fixed displacement axial piston motors, featuring a swashplate axial piston design with valve plate flow distribution, suitable for hydrostatic drives in both open and closed circuits. The 74318 Series covers displacements from 32.9 to 40.6 cm³/rev, with a nominal pressure rating of 350 bar (5,076 psi) and maximum speed of 3,600 rpm, renowned for its compact construction, high volumetric efficiency (up to 96%), and excellent power-to-weight ratio in mobile machinery and industrial drive applications.
In the model code 74318-DAH, 74318 designates the 743 Series medium-duty fixed motor with 40.6 cm³/rev displacement; DAH is the configuration code defining the output shaft, port location, mounting flange, and special feature options. The motor is manufactured to original Danfoss specifications with 100% drop-in interchangeability, requiring no modification to mounting interfaces, port positions, or hydraulic connections. Every unit undergoes 100% simulated operating condition testing at the factory, including rated pressure loading, volumetric efficiency verification, seal integrity assessment, and low-speed smoothness validation prior to shipment.
Technical Specifications
74318-DAH:
Series / Type: Danfoss 74318 Series medium-duty fixed displacement axial piston motor, valve plate design
Displacement: 40.6 cm³/rev (2.48 in³/rev)
Design: Swashplate axial piston, fixed displacement, valve plate flow distribution
Nominal pressure (continuous): 350 bar (5,076 psi / 35 MPa)
Maximum pressure (intermittent): 370 bar (5,400 psi)
Peak pressure: 400 bar (5,800 psi)
Rated speed: 3,600 rpm
Maximum speed: 3,600 rpm
Output flow at rated speed: 40.6 gpm (153.7 L/min)
Output power at rated speed and pressure: 58 hp (approx. 43.3 kW)
Rated torque: 226.27 Nm (2,004.54 lb-in)
Direction of rotation: Bidirectional (either A or B port as inlet; rotation reversed simply by reversing flow direction)
Mounting: SAE-B 2-bolt flange
Output shaft: 13-tooth, 16/32 pitch spline
Main ports: SAE-16 O-ring ports
Drain port: SAE-8, top of housing
Continuous allowable case pressure: 1.7 bar (25 psi)
Continuous inlet temperature: 107°C (225°F)
Housing material: High-strength cast iron
Approximate weight: 9.1 kg (20 lb)
Note: Technical data above is sourced from Danfoss official product data sheets and authorized distributor specifications. For precise configuration parameters of the 74318-DAH, always confirm against the official Danfoss technical manual or the product nameplate.
743 Series displacement range (for reference):
74315: 32.9 cm³/rev (2.01 in³/rev), rated speed 3,600 rpm, rated torque 183.36 Nm
74318: 40.6 cm³/rev (2.48 in³/rev), rated speed 3,600 rpm, rated torque 226.27 Nm
74328: 40.6 cm³/rev (high-torque configuration), rated torque 246.78 Nm
74348: 40.6 cm³/rev (tandem configuration)
Note: The 743 Series shares the medium-duty fixed axial piston motor platform with the 741 Series (displacements from 12.3 to 20.3 cm³/rev), with both series sharing valve plate design and certain core rotating group components.
Key Technical Advantages
1. Swashplate Axial Piston Design with High Volumetric Efficiency
The 74318-DAH employs a swashplate axial piston design with precision-lapped piston-to-bore pairs and valve plate flow distribution, achieving volumetric efficiency up to 96% and overall efficiency up to 90%. Compared to gear or vane motors, the axial piston design accommodates higher working pressures (350 bar vs. 210 bar) within the same envelope, with volumetric efficiency maintained across a wide speed range. The motor can operate continuously, intermittently, in reversing mode, or even stalled without damage, providing exceptional duty cycle adaptability.
2. High Power Density and Compact Construction
The 74318-DAH achieves 40.6 cm³/rev displacement capability and 350 bar working pressure in a unit weighing only approximately 9.1 kg, delivering a power-to-weight ratio that leads its class among medium-duty motors. The compact swashplate design enables high torque output within limited installation space, particularly suited to space-constrained mobile machinery and industrial drive applications. The motor is specifically designed for applications requiring constant rotary motion at a distance from the power source.
3. Bidirectional Rotation for System Simplification
Both main ports are functionally symmetrical, allowing either port to serve as inlet or outlet. Rotation direction is reversed simply by reversing the direction of flow through the motor ports, without requiring internal reversing mechanisms or external valve groups. In hydrostatic travel drives, vehicle direction is controlled solely by the pump swashplate angle — the motor requires no adjustment to change direction. This simplifies system control logic and eliminates a potential failure point in the hydraulic circuit.
4. Extensive Configuration Options for System Integration Flexibility
The 74318 Series offers multiple shaft configurations (13-tooth or 15-tooth spline), port locations (side or rear), mounting flanges, and auxiliary valve options (such as shuttle valves, back pressure valves, and speed sensors), providing flexible adaptation for system integration. Optional shuttle and back pressure valves improve loop cooling and flushing; the speed sensor detects speeds as low as 50 rpm. For equipment manufacturers requiring multiple drive configurations, this design significantly simplifies spare parts management and system integration complexity.
Application Areas
Agricultural machinery: Combine harvester ground drives, self-propelled sprayers, seeders, mowers, tractor auxiliary drives
Forestry equipment: Log skidders, forestry harvesters
Construction equipment: Skid steer loaders, aerial work platforms, forklift travel drives, mini excavators
Municipal equipment: Street sweepers, snow removal equipment
Turf care equipment: Commercial mowers, golf course maintenance equipment
Industrial applications: Constant-speed industrial hydraulic drive systems, fan drives
Expert Maintenance Tips
1. Case Filling and Air Purging — The First Step Before Startup
Before first startup, the motor case must be filled with system fluid through the uppermost drain port until fluid overflows. The housing must be kept full at all times to provide internal lubrication. Case pressure must never exceed 5 psi (0.35 bar); continuous allowable case pressure is 1.7 bar (25 psi). Excessive case pressure will cause shaft seal failure and housing deformation.
2. Fluid Cleanliness Management
The 74318-DAH operates with micron-level clearances between pistons and cylinder bores and between the valve plate and cylinder block face. Systems must be equipped with filtration rated to ISO 4406 18/16/13 or better. In high-contamination agricultural or construction environments, consider shortening fluid change intervals accordingly. Continuous inlet temperature must not exceed 107°C (225°F).
3. Case Drain Line Configuration Requirements
Case drain must be routed to the reservoir through the highest drain port, terminating below the minimum oil level in the reservoir to maintain positive return flow under all operating conditions. The drain line must remain unobstructed, free from any form of restriction or blockage.
4. Output Shaft Spline and Mounting Alignment
The 74318-DAH features a 13-tooth, 16/32 pitch spline output shaft. During installation, verify that the spline is properly aligned with the mating component, and that spline engagement length meets design requirements. Installation misalignment will cause abnormal spline wear and bearing side loading, significantly shortening service life. Tighten mounting bolts in stages to the standard torque value for SAE-B 2-bolt flange mounting, and re-check torque after 500 operating hours.
5. Flexible Application of Bidirectional Rotation
Since the motor is capable of bidirectional rotation, installation orientation relative to rotation direction is not a constraint. However, in closed-circuit applications, ensure that the flushing valve (if equipped) is oriented to match the main circuit for effective case flushing and heat exchange.
6. Restart Procedure After Extended Shutdown
If the motor has been idle for more than three months, manually rotate the output shaft to confirm freedom of movement, and inspect the case oil level and shaft seal for leakage before restarting. Extended shutdown can cause oil film drainage from piston-slipper interfaces, creating a dry-start risk. Before restarting, replenish clean hydraulic fluid through the case fill port and operate at low speed and reduced load for 10–15 minutes before returning to normal duty.
