Sauer Danfoss 51D110 Variable Displacement Motor 51D110-1 Bent Axis Motor Replacement
Wuhan Xinlaifu Hydraulic Equipment Co., Ltd. is one of the leading manufacturers and suppliers of sauer danfoss 51d110 variable displacement motor 51d110-1 bent axis motor replacement in China. With abundant experience, we warmly welcome you to buy high quality customized products at competitive price from our factory. Also, OEM&ODM service is available.
Specifications
| Parameter | 51D110-1 |
|---|---|
| Series | Series 51 / 51-1 (51D) |
| Displacement | 110 cc/rev (109.9 cc/rev) |
| Rated (Nominal) Pressure | 480 bar (7000 psi) |
| Maximum Pressure | 510 bar (7400 psi) |
| Minimum Input Pressure | 10 bar (145 psi) |
| Rated Speed | 2200–5600 rpm |
| Max Speed Range | up to 7000 rpm |
| Specific Torque (at max disp) | ≈ 0.35 N·m/bar (≈1067 lbf·in per 1000 psi) |
| Mounting Type | SAE 4-bolt flange (ISO 3019/1) / 2-bolt cartridge |
| Direction of Rotation | Bi-directional |
| Temperature Range | -40 °C to 115 °C |
| Typical Application | Hydrostatic transmission drives (replacement motor) |
Product Overview
Danfoss 51D110 Series Variable Displacement Motor – Bent Axis Motor for Closed Circuit Drives
When a road roller, telescopic handler, or compact track loader loses its drive motor, the machine stops moving. On a Bomag BW 156 D-3 working a compaction pass, a Merlo P28.7 KT on a construction site, or a Bobcat T2556 in a tight load-out area, a failed travel motor means the machine is parked until a replacement arrives.
The Danfoss 51D110 is a bent axis variable displacement axial piston motor from the Series 51 / 51-1 platform. It is designed for closed circuit hydrostatic drives, where it operates as the final drive unit - converting hydraulic pressure into rotary torque at the wheel, drum, or track sprocket.
What makes the 51D110 different from a standard hydraulic motor?
The 51D110 uses a bent axis design with spherical pistons. The cylinder block is angled relative to the output shaft, and the pistons act directly against a thrust plate. This architecture delivers high starting torque and smooth operation across the full speed range - from 0 rpm to the maximum rated speed.
The displacement ratio is the key selection parameter. The 51D110 has a maximum displacement of 109.9 cm³/rev and a minimum of 22 cm³/rev - a 5:1 ratio. In practice, this means the motor can operate at high displacement for maximum torque (climbing grades, heavy compaction) and then shift to low displacement for higher speed (traveling on flat ground). The shift occurs under load, without changing pump output.
Which 51D110 do you need? The two model codes on this page differ in control configuration and displacement limiter setting:
| Model Code | Control Configuration | Displacement Limiter | Primary Application |
|---|---|---|---|
| 51D110-1-RD3NE1B1NNU1NNN053AAF00000 | RD3N / E1B1 control | 053 setting | Bomag BW 156 D-3, Merlo P28.7 KT |
| 51D110-1-RD4NN1NNNNU1NNN035AAF30000 | RD4N / N1 control | 035 setting | Bobcat T2556, other Series 51-1 applications |
Selection rule: Match the model code from your original motor's nameplate. The control configuration (RD3N vs RD4N, E1B1 vs N1) determines how the motor responds to the machine's control signal. Installing a motor with the wrong control configuration will change drive behavior - the machine may not shift speeds correctly, or the travel system may not respond as expected.
Core Advantages
1. Two Model Codes – Match the Configuration to Your Machine
The two model codes listed on this page are not interchangeable without verification. Each encodes a specific control type and displacement limiter setting.
51D110-1-RD3NE1B1NNU1NNN053AAF00000
This configuration is associated with Bomag BW 156 D-3 and Merlo P28.7 KT applications. The RD3N control designation indicates a specific hydraulic control interface, and the 053 displacement limiter sets the maximum displacement to a specific value within the 109.9 cm³ range. The E1B1 code identifies the control variant used in these machines.
51D110-1-RD4NN1NNNNU1NNN035AAF30000
This configuration uses the RD4N control designation with N1 control - a different hydraulic control interface from RD3N. The 035 displacement limiter setting differs from the 053 configuration, and the NNNN code indicates a different porting and adjustment configuration.
Before ordering: Read the model code from your original motor's nameplate. The suffix after the dash determines the control type and displacement limiter. A motor with the correct base displacement but the wrong control suffix will not integrate correctly with your machine's hydrostatic system.
2. Control Options – N1, HZ, E1, E2, E7, EP, EQ, D7, D8, HS
The 51D110 is available with a wide range of control options. The control determines how the motor's displacement is adjusted - from simple two-position hydraulic control to electronic proportional control.
| Control Code | Type | Best For |
|---|---|---|
| N1 | Hydraulic proportional control | Standard mobile equipment, direct operator control |
| HZ | Hydraulic two-position control | Machines with simple high/low speed selection |
| E1 / E2 / E7 | Electronic proportional control | Machines with electronic joystick or PLC control |
| EP / EQ | Electronic proportional control (specific variants) | Precision drive control applications |
| D7 / D8 | Hydraulic control variants | Specific OEM configurations |
| HS | Hydraulic control | Standard hydrostatic drive systems |
How the controls work: The 51D110 is equipped with an integrated pressure compensator that functions when the motor operates in both motor and pump modes. The controls may utilize internally supplied servo pressure. A pressure compensator override - with optional defeat function - prevents the compensator from engaging when the motor is running in pump mode.
Selection guidance: If your machine uses a simple high/low speed selector, an HZ or hydraulic control is appropriate. If your machine has an electronic joystick or CAN bus control system, E1, E2, or E7 electronic proportional control is required. Confirm the control code from your original motor before ordering.
3. Displacement Limiter – Why 053 vs 035 Matters
The displacement limiter setting at the end of the model code (053 vs 035) controls the maximum displacement the motor can achieve. This directly affects the maximum torque the motor can produce.
| Model Code Suffix | Displacement Limiter | Effect |
|---|---|---|
| 053 | Higher limiter setting | Higher maximum torque, lower maximum speed |
| 035 | Lower limiter setting | Lower maximum torque, higher maximum speed |
Practical impact: On a Bomag roller, the 053 setting provides the torque required for drum or wheel drive under compaction load. On a Bobcat T2556, the 035 setting may be matched to a different drive system requirement. Do not assume the two limiters are interchangeable - using a motor with the wrong limiter setting will change the machine's drive characteristics.
4. Built for Closed Circuit Systems – Motor and Pump Mode Capability
The 51D110 is designed specifically for closed circuit hydrostatic drives. It operates with other components in the closed loop to transmit and control hydraulic power.
What this means for your system: In a closed circuit, the motor receives flow from a variable displacement pump and returns flow to the pump inlet - rather than to a reservoir. The motor must maintain proper case pressure and lubrication under all operating conditions. The 51D110's integrated flushing valve and pressure compensator are designed for this duty.
Motor and pump mode: The 51D110 can operate as a motor (converting hydraulic power to mechanical power) or as a pump (converting mechanical power to hydraulic power during braking). The pressure compensator functions in both modes, and the optional defeat function prevents compensator engagement when the unit is running in pump mode.
5. Confirmed Machine Compatibility – Bomag, Merlo, Bobcat
The 51D110 is documented as the original equipment motor for several machine platforms.
Bomag BW 156 D-3: The wheel drive motor is a Sauer-Sundstrand series 51 D 110 axial piston motor with variable displacement. The DH/PDH versions use the same motor as the drum drive motor, with a different connecting housing. This confirms the 51D110 as the correct replacement for both wheel and drum drive functions on BW 156 D-3 variants.
Merlo P28.7 KT: The drive motor unit is listed as Danfoss 51D110 AD3N, part number 046AAA01328. This provides a specific OEM part number for cross-reference when ordering a replacement.
Bobcat T2556: The drive motor is identified as Sauer-Danfoss 51D110 in multiple parts listings. Bobcat also lists replacement hydraulic motors under part numbers 6916977 and 6916978 for the T2556 and related models.
Other applications: The Series 51 motor family is used in tracked dozer drives, road construction machinery, wheel drive or running gear of railway equipment, and winches.
6. Technical Specifications at a Glance
| Parameter | Value |
|---|---|
| Maximum displacement | 109.9 cm³/rev (6.71 in³/rev) |
| Minimum displacement | 22 cm³/rev (1.34 in³/rev) |
| Displacement ratio | 5:1 |
| Rated pressure | 480 bar (48 MPa) |
| Maximum pressure | 510 bar (51 MPa) |
| Rated flow | 308 L/min (81 US gal/min) |
| Maximum flow | 396 L/min (105 US gal/min) |
| Maximum speed | 5600 rpm |
| Mass moment of inertia | 0.0128 kgm² (0.3037 lb·ft²) |
| Maximum corner power | 492 kW (660 hp) |
| Weight (approx.) | 44 kg (97 lb) |
| Mounting | Four-bolt SAE or DIN flange; two-bolt cartridge configuration |
| Main pressure ports | SAE flange |
| Other ports | SAE straight thread O-ring boss |
Operating note: All Series 51 motors start at full displacement. This means the motor delivers maximum starting torque on demand, which is essential for accelerating a loaded machine from rest - a road roller beginning a compaction pass, or a telescopic handler lifting a load from a standstill.
Q1: What is the difference between the two model codes on this page?
| 51D110-1-RD3NE1B1NNU1NNN053AAF00000 | 51D110-1-RD4NN1NNNNU1NNN035AAF30000 | |
|---|---|---|
| Control designation | RD3N with E1B1 control | RD4N with N1 control |
| Displacement limiter | 053 | 035 |
| Port/adjustment code | NNU1 | NNNU1 |
| Typical application | Bomag BW 156 D-3, Merlo P28.7 KT | Bobcat T2556, other Series 51-1 machines |
They are not interchangeable without verification. The control configuration and displacement limiter must match your machine's original motor. Read the model code from your motor's nameplate before ordering.
Q2: What are the key technical specifications of the 51D110?
| Parameter | Value |
|---|---|
| Maximum displacement | 109.9 cm³/rev |
| Minimum displacement | 22 cm³/rev |
| Displacement ratio | 5:1 |
| Rated pressure | 480 bar |
| Maximum pressure | 510 bar |
| Rated flow | 308 L/min |
| Maximum flow | 396 L/min |
| Maximum speed | 5600 rpm |
| Maximum corner power | 492 kW |
| Weight | Approximately 44 kg |
| Mounting | Four-bolt SAE/DIN flange or two-bolt cartridge |
Q3: What control options are available for the 51D110?
The 51D110 supports a wide range of controls: N1, HZ, E1, E2, E7, F1, F2, T1, T2, TA, TH, EP, EQ, L1, L2, L7, D7, D8, HS.
Hydraulic controls (N1, HZ, D7, D8, HS): For machines with hydraulic pilot control - joysticks or lever-operated systems.
Electronic proportional controls (E1, E2, E7, EP, EQ): For machines with electronic joystick or PLC control systems.
Two-position controls (HZ, F1, F2): For simple high/low speed selection.
How to choose: Confirm the control code from your original motor's nameplate. The control code is embedded in the full model number - for example, "E1B1" in the RD3NE1B1 configuration indicates electronic proportional control.
Q4: Can I replace a 51D110 with a different Series 51 displacement?
Not recommended without system verification. The 51D110 has a specific displacement (109.9 cm³) matched to the machine's hydrostatic pump output and drive requirements. A larger displacement (e.g., 51D160) would provide more torque but require more flow - potentially overloading the pump or changing the machine's speed characteristics. A smaller displacement (51D080) would reduce torque and may not meet the machine's drive requirements.
For a drop-in replacement that restores original performance: Order the 51D110 with the correct control code and displacement limiter setting from your machine's parts documentation.
Q5: What OEM part numbers cross-reference to the 51D110?
| OEM Number | Associated Machine / Application |
|---|---|
| 80004866 | 51D110-1-RD3N E2B1 NNU1 NNN 050AAF3 0000 |
| 046AAA01328 | Merlo P28.7 KT drive motor unit (51D110 AD3N) |
| 6916977 / 6916978 | Bobcat T2556 and related telescopic handler hydraulic motors |
Use the part number from your machine's parts manual for the most reliable cross-reference. The full 51D110 model code on your original motor's nameplate is the definitive identifier.
Q6: What should I check before installing a replacement 51D110?
Six items before installation:
Full model code - Confirm the control code (RD3N vs RD4N, E1B1 vs N1) and displacement limiter (053 vs 035) match your original motor.
Mounting flange - Four-bolt SAE/DIN or two-bolt cartridge. Verify the bolt pattern and pilot diameter match your drive housing.
Shaft and coupling - Confirm the output shaft spline or key matches your wheel hub or gearbox input.
Port layout - Main pressure ports are SAE flange; remaining ports are SAE straight thread O-ring boss. Confirm port positions match your piping.
Case drain routing - The case drain must return to the reservoir without restriction. Maximum case pressure limits apply - consult the service manual for your specific machine.
Servo pressure source - The controls may utilize internally supplied servo pressure. Confirm the servo supply configuration matches your system.
Q7: Do you provide test reports?
Yes. Each 51D110 motor undergoes factory testing before shipment, including displacement verification, pressure/torque performance data, and internal leakage measurement. Test data and videos are available upon request.
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