A4VG28 A4VG56 A4VG71 A4VG90 A4VG125 Piston Pump | 400 bar | Rexroth

Product Overview

The A4VG series swashplate axial piston variable pumps represent a core product line within the Bosch Rexroth closed-circuit hydraulic transmission platform, featuring the proven swashplate axial piston design specifically developed for closed-circuit hydrostatic drive systems. The series offers eight displacement sizes from 28 to 250, covering applications from compact to heavy-duty mobile equipment. This product covers five mainstream displacement models — A4VG28, A4VG56, A4VG71, A4VG90, and A4VG125 — with the A4VG28HD3DMT/32L-NSC10F003D-S serving as the 28cc mainstream model.

Control Description: The A4VG28HD3DMT/32L-NSC10F003D-S features HD3DMT control — Hydraulic Proportional Control where pump displacement is proportional to pilot pressure. This control offers rapid response and precise regulation, making it ideal for traction drive and implement applications requiring frequent displacement adjustments.

100% Interchangeability Guarantee: Our pumps strictly adhere to Bosch Rexroth A4VG Series 32 original mounting dimensions and port layouts, enabling drop-in replacement without modifications. Every unit undergoes 100% simulated duty-cycle testing under actual load conditions to validate performance parameters before shipment, ensuring immediate reliability upon installation.

Quality & Manufacturing Standards: The housing is manufactured from high-strength cast iron, with critical tribological pairs (cylinder barrel/valve plate, pistons/slippers) precision-ground and heat-treated. An integrated boost pump serves the dual purpose of providing boost and pilot oil supply. Each high-pressure side is equipped with two relief valves that also function as boost inlet valves to prevent hydrostatic transmission overload. An adjustable pressure cutoff is standard. Through drive enables mounting of additional pumps up to the same nominal size.

Technical Specifications 

Series General Specifications (A4VG Series 32):

• Design: Swashplate axial piston variable pump

• Circuit Type: Closed circuit (hydrostatic transmission)

• Rated Pressure: 400 bar (40 MPa)

• Maximum Pressure: 450 bar (45 MPa)

• Flow Reversal: Smooth direction change when swashplate crosses neutral

• Integrated Boost Pump: Supplies both boost and pilot oil

• Pressure Cutoff: Adjustable, standard feature

• Through-Drive: Supports mounting of additional same-size pumps

• Control Options: Multiple (NV no control, DG direct, HD hydraulic proportional, HW mechanical servo, EP electric proportional, EZ electric two-point, DA speed-related, etc.)

A4VG28 (A4VG28HD3DMT/32L-NSC10F003D-S):

• Displacement (Vg max): 28.0 cm³/rev

• Boost Pump Displacement (@ 20 bar): 6.1 cm³/rev

• Rated Pressure: 400 bar

• Maximum Pressure: 450 bar

• Maximum Speed @ Vg max: 4,250 rpm

• Maximum Limited Speed: 4,500 rpm

• Maximum Intermittent Speed: 5,000 rpm

• Minimum Speed: 500 rpm

• Maximum Flow (@ nmax & Vg max): 119 L/min

• Power (@ nmax, Vg max, Δp=400 bar): 79 kW

• Torque (@ Vg max, Δp=400 bar): 178 N·m

• Torque (@ Δp=100 bar): 44.5 N·m

• Moment of Inertia: 0.0022 kg·m²

• Max. Shell Capacity: 0.9 L

• Weight (approx.): 29 kg

• Control Type: HD3DMT (Hydraulic Proportional Control)

A4VG56:

• Displacement (Vg max): 56.0 cm³/rev

• Boost Pump Displacement (@ 20 bar): 11.6 cm³/rev

• Rated Pressure: 400 bar

• Maximum Pressure: 450 bar

• Maximum Speed @ Vg max: 3,600 rpm

• Maximum Limited Speed: 3,900 rpm

• Maximum Intermittent Speed: 4,500 rpm

• Minimum Speed: 500 rpm

• Maximum Flow (@ nmax & Vg max): 202 L/min

• Power (@ nmax, Vg max, Δp=400 bar): 134 kW

• Torque (@ Vg max, Δp=400 bar): 356 N·m

• Torque (@ Δp=100 bar): 89 N·m

• Moment of Inertia: 0.0066 kg·m²

• Max. Shell Capacity: 1.5 L

• Weight (approx.): 38 kg

A4VG71:

• Displacement (Vg max): 71.0 cm³/rev

• Boost Pump Displacement (@ 20 bar): 19.6 cm³/rev

• Rated Pressure: 400 bar

• Maximum Pressure: 450 bar

• Maximum Speed @ Vg max: 3,300 rpm

• Maximum Limited Speed: 3,600 rpm

• Maximum Intermittent Speed: 4,100 rpm

• Minimum Speed: 500 rpm

• Maximum Flow (@ nmax & Vg max): 234 L/min

• Power (@ nmax, Vg max, Δp=400 bar): 156 kW

• Torque (@ Vg max, Δp=400 bar): 452 N·m

• Torque (@ Δp=100 bar): 113 N·m

• Moment of Inertia: 0.0097 kg·m²

• Max. Shell Capacity: 1.3 L

• Weight (approx.): 50 kg

A4VG90:

• Displacement (Vg max): 90.0 cm³/rev

• Boost Pump Displacement (@ 20 bar): 19.6 cm³/rev

• Rated Pressure: 400 bar

• Maximum Pressure: 450 bar

• Maximum Speed @ Vg max: 3,050 rpm

• Maximum Limited Speed: 3,300 rpm

• Maximum Intermittent Speed: 3,800 rpm

• Minimum Speed: 500 rpm

• Maximum Flow (@ nmax & Vg max): 275 L/min

• Power (@ nmax, Vg max, Δp=400 bar): 183 kW

• Torque (@ Vg max, Δp=400 bar): 573 N·m

• Torque (@ Δp=100 bar): 143 N·m

• Moment of Inertia: 0.0149 kg·m²

• Max. Shell Capacity: 1.5 L

• Weight (approx.): 60 kg

A4VG125:

• Displacement (Vg max): 125.0 cm³/rev

• Boost Pump Displacement (@ 20 bar): 28.3 cm³/rev

• Rated Pressure: 400 bar

• Maximum Pressure: 450 bar

• Maximum Speed @ Vg max: 2,850 rpm

• Maximum Limited Speed: 3,250 rpm

• Maximum Intermittent Speed: 3,450 rpm

• Minimum Speed: 500 rpm

• Maximum Flow (@ nmax & Vg max): 356 L/min

• Power (@ nmax, Vg max, Δp=400 bar): 237 kW

• Torque (@ Vg max, Δp=400 bar): 796 N·m

• Torque (@ Δp=100 bar): 199 N·m

• Moment of Inertia: 0.0232 kg·m²

• Max. Shell Capacity: 2.1 L

• Weight (approx.): 80 kg

Key Technical Advantages

1. Over-Center Swashplate — Smooth, Shock-Free Flow Reversal
The A4VG series allows the swashplate to move through the neutral position (over center), enabling smooth flow direction changes. This means that in traction drive applications, forward and reverse transitions are seamless without additional directional valves. Compared to conventional directional valve switching, over-center swashplate reversal delivers shock-free, pressure-surge-free flow reversal — significantly improving ride comfort and system longevity.

2. Integrated Boost Pump and Pilot Supply — Highly Integrated Design
The A4VG series features an integrated boost pump that serves the dual purpose of providing boost and pilot oil supply. This highly integrated design drastically reduces external piping and accessory requirements, lowering system leakage risks and installation/maintenance costs. Maximum boost pressure is precisely limited by a built-in boost relief valve.

3. High-Pressure Relief Valves with Boost Function — Dual System Protection
Each high-pressure side is equipped with two relief valves that also function as boost inlet valves. These provide overload protection when system pressure exceeds limits and boost function when vacuum conditions occur. This ensures dual safety protection for the hydrostatic transmission (pump and motor).

4. Adjustable Pressure Cutoff as Standard — Dual Safety Assurance
The A4VG series features an adjustable pressure cutoff as standard. When system pressure reaches the set value, the pressure cutoff reduces pump displacement to zero, ensuring system pressure never exceeds the safety threshold. Cutoff pressure is field-adjustable per application requirements, providing reliable overpressure protection.

5. Through-Drive — Unlimited System Expansion
The A4VG series features standard through-drive capability for mounting additional same-nominal-size pumps. This enables the A4VG series to serve as the “power core” of complex hydraulic systems — driving multiple circuits from a single pump without additional power input interfaces or transfer cases.

6. Extensive Control Options — Full-Scenario Adaptability
The A4VG series offers a wide range of highly compatible control devices, including NV (no control), DG (direct), HD (hydraulic proportional), HW (mechanical servo), EP (electric proportional), EZ (electric two-point), DA (speed-related), and more. The HD3DMT hydraulic proportional control featured in this product offers rapid response and precise regulation, with pump displacement proportional to pilot pressure.

Application Areas

The A4VG series swashplate axial piston variable pumps are widely deployed in closed-circuit hydrostatic drive systems across the following applications:

• Tracked and Wheeled Construction Machinery — traction drive systems for excavators, bulldozers, loaders

• Agricultural Machinery — hydrostatic drives for combine harvesters, tractors, windrowers

• Road Construction Machinery — traction drives for asphalt pavers and rollers

• Material Handling Equipment — traction and implement drives for heavy forklifts and reach stackers

• Mining Equipment — hydrostatic traction drives for underground loaders and haulers

• Specialty Vehicles — hydrostatic transmissions for military vehicles and airport ground support equipment

• Industrial Applications — closed-circuit applications such as test benches and winch drives

Expert Maintenance Tips

1. Housing Priming Before Installation (Critical Step)
Before initial start-up or after extended downtime, the housing must always be filled with hydraulic fluid. Pre-fill through case drain ports prior to start-up. Dry-running at start-up will cause irreversible damage to critical tribological pairs (cylinder barrel/valve plate, pistons/slippers).

2. Charge Pressure Monitoring
The A4VG series relies on the integrated boost pump for charge pressure and pilot oil supply. Continuously monitor charge pressure during operation to ensure it meets specifications. Insufficient charge pressure will result in sluggish control response, inadequate lubrication, and potential pump failure.

3. Filtration and Fluid Cleanliness
The A4VG series is designed for operation with HLP mineral oil per DIN 51524. Axial piston pumps are highly sensitive to fluid cleanliness — recommended filtration per ISO 4406 cleanliness level of 19/17/14 or better. Return line and suction filters should be inspected and replaced regularly.

4. Through-Drive Tandem Installation Considerations
For tandem installations on the through-drive, arrange the highest power flow unit closest to the input power source. Ensure all case drain ports in the tandem stack have unrestricted return paths to prevent case pressure exceedance.

5. Initial Start-Up and Break-In
For first-time operation, run the pump at low speed (idle) with no load for 5–10 minutes to purge air from the system and allow proper oil film establishment on all tribological pairs before gradually applying load.

6. HD3DMT Control Tuning Considerations
HD3DMT hydraulic proportional control regulates pump displacement via pilot pressure signals. During commissioning, systematically set the pilot pressure range and corresponding displacement characteristic curve per the technical manual (data sheet RE 92003).