90M055NC0N7N0S1W00NNN0000F0 Danfoss Sauer Series 90M Fixed Motor 55cc 450Bar

Product Overview

The Series 90M fixed displacement axial piston motor represents a field-proven hydraulic drive solution within the Sauer Danfoss Series 90 platform, engineered specifically for closed-circuit hydrostatic transmission systems in mobile and industrial applications. The motor features a parallel axial piston/slipper design with a fixed swashplate, enabling bidirectional operation with either port serving as inlet or outlet, and delivering a constant ratio between pump input flow and shaft output speed.

The specific model covered in this document — 90M055NC0N7N0S1W00NNN0000F0 — is the 55 cm³/rev configuration with SAE flange mounting and integrated loop flushing. It is manufactured to original Sauer 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, case pressure validation, and seal integrity assessment prior to shipment.

Technical Specifications 

90M055NC0N7N0S1W00NNN0000F0:

• Series / Type: Series 90M fixed displacement axial piston motor

• Displacement: 55 cm³/rev (3.35 in³/rev)

• Design: Parallel axial piston/slipper with fixed swashplate

• Rated working pressure: 420 bar (6,090 psi)

• Maximum working pressure: 450 bar (6,525 psi)

• Peak pressure: 480 bar (6,960 psi)

• Continuous speed at max. displacement: 3,900 rpm

• Maximum speed: 4,250 rpm

• Minimum speed: 500 rpm

• Direction of rotation: Bidirectional (either A or B port as inlet)

• Mounting flange: SAE flange mount (MF type)

• Control type: NC type (no displacement control, fixed displacement)

• Displacement setting: 7 (standard displacement configuration)

• Loop flushing: S1 configuration (with flushing provision)

• Theoretical torque: 0.88 Nm/bar

• Housing material: High-strength ductile cast iron

• Circuit type: Closed-loop hydrostatic

• Approximate weight: 22 kg

Series 90M displacement range (for reference):

• 90M042: 42 cm³/rev

• 90M055: 55 cm³/rev

• 90M075: 75 cm³/rev

• 90M100: 100 cm³/rev

• 90M130: 130 cm³/rev

The Series 90M motor shares a substantial number of components with the Series 90 pump line, including pistons, slippers, cylinder block, valve plate, and bearings. This parts-unification strategy simplifies spare parts management and reduces lead times for repair components.

Key Technical Advantages

1. Parallel Axial Piston/Slipper Design with Fixed Swashplate
The 90M Series employs a parallel axial piston and slipper arrangement operating against a fixed-angle swashplate. The fixed displacement architecture eliminates the control mechanism response lag and regulation deviations inherent in variable displacement designs, delivering superior operating stability and repeatability under sustained load conditions. Precision-matched piston-slipper pairs maintain a consistent oil film under high pressure, preserving high volumetric efficiency and minimizing internal leakage across the full operating envelope.

2. High Pressure Rating and Structural Load Capacity
The motor is rated for continuous operation at 420 bar, with a maximum working pressure of 450 bar and a peak pressure capability of 480 bar. The high-strength ductile iron housing and reinforced shaft/bearing assembly enable the motor to withstand the frequent pressure spikes and vibration loads characteristic of construction and agricultural duty cycles. For applications involving cyclic shock loading — such as combine harvester ground drives and vibratory roller travel systems — this structural design margin significantly extends service life under demanding field conditions.

3. Bidirectional Operation with Symmetrical Port Design
Both main ports (A and B) are functionally symmetrical, allowing either port to serve as inlet or outlet without internal reversing mechanisms. In hydrostatic travel drives, vehicle direction is controlled solely by the pump swashplate angle — the motor requires no adjustment or valving to change direction. This simplifies system control logic and eliminates a potential failure point in the hydraulic circuit.

4. Integrated Loop Flushing Provision (S1 Configuration)
The “S1” designation in the model code indicates the motor is equipped with a loop flushing provision. In closed-circuit operation, the flushing valve continuously draws a small volume of hot oil from the low-pressure side of the loop, routing it through the motor case to the reservoir. This feature removes heat and wear debris from the motor interior, helping to maintain case oil temperature within acceptable limits and preserve fluid cleanliness — particularly important for agricultural and construction equipment operating continuously under load in high-ambient-temperature environments.

5. Component Commonality with Series 90 Pumps
The Series 90M motor shares critical rotating group components — including pistons, slippers, cylinder block, valve plate, and bearings — with the Series 90 variable displacement pump platform. The engineering value of this commonality is twofold: repair parts can be sourced from the same inventory as pump components, reducing spare parts complexity; and reliability validation accumulated over decades of pump operation transfers directly to the motor, enhancing fleet-level maintenance economics.

Application Areas

• Combine harvester ground drives: John Deere 6600/6620/7700/7720, Claas Dominator 76/86/96, New Holland TR70/TR75, Case IH 1460/1480 hydrostatic travel systems

• Soil compactors: Bomag BW120 AD/BW138 AD, Dynapac CA252, Ammann ASC 110 vibratory roller travel drives

• Forestry forwarders: Timberjack 1010B and comparable forwarder hydrostatic travel systems

• Agricultural machinery: Self-propelled sprayers, windrowers, sugar beet harvesters

• Industrial applications: Transit mixer drum drives, specialty vehicle hydrostatic transmissions

Expert Maintenance Tips

1. Closed-Loop Flushing Flow and Case Pressure Control
The S1 flushing configuration requires verification that the flushing circuit is unobstructed and that case drain back pressure remains within specified limits. Case pressure should be maintained in the 2–3 bar range. Excessive case pressure will damage the shaft seal; insufficient pressure will reduce flushing effectiveness. The flushing valve setting should be matched to system heat rejection requirements, and case oil temperature should be monitored to remain below 90°C under sustained heavy-duty operation.

2. Fluid Cleanliness Is the Primary Service Life Determinant
The 90M Series 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. Replace filter elements at the first 500-hour interval, then every 1,000–2,000 hours or based on oil analysis results. In high-contamination environments such as agricultural or construction job sites, consider shortening the fluid change interval accordingly.

3. Pre-Start Case Filling and Air Purging
Before first startup after installation or repair, the motor case must be filled with clean hydraulic fluid through the highest case port until fluid overflows. Starting an un-purged motor can cause dry friction between piston-slipper pairs and bearings, leading to premature wear. For units equipped with a flushing valve, verify that the flushing circuit establishes normal circulation after filling.

4. Spline Shaft and Mounting Flange Alignment
When installing with SAE flange mounting, verify that the motor output spline is properly aligned with the mating component. Spline engagement length should meet design requirements, and angular misalignment must be avoided to prevent abnormal spline wear and bearing side loading. Tighten mounting bolts in stages to the specified torque value, and re-check torque after 500 operating hours. Always use the correct O-ring seal at the flange interface.

5. Monitor Case Drain Flow and Temperature as Wear Indicators
Case drain flow rate and oil temperature are sensitive indicators of internal motor condition. A progressive increase in case drain flow or sustained elevated case oil temperature may indicate piston-slipper wear, valve plate sealing degradation, or bearing deterioration. Record a baseline case flow and temperature under normal operating conditions quarterly to enable trend-based condition monitoring.

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.