Rexroth A4VG series 32 axial piston variable hydraulic pump

The A4VG is a variable-displacement axial piston pump in swashplate design, built by Bosch Rexroth specifically for closed-circuit hydrostatic transmissions. In plain terms, it pairs with a hydraulic motor (commonly an A6VM or A10FM-type motor) to deliver stepless, reversible drive without a gearbox doing the speed changes.

Series 32 is a specific generation of this pump family. It sits between the older series (such as 71) and the later series 40, and it remains widely installed and widely supported in the aftermarket.

Key specifications at a glance

• Design: Axial piston, swashplate, variable displacement
• Circuit type: Closed circuit (hydrostatic transmission)
• Sizes: Commonly listed from 28 up to 250 (displacement in cm³ per revolution)
• Pressure rating: Nominal pressure of 400 bar with peak pressure up to 450 bar (confirm against the datasheet for your exact size and operating condition)
• Flow direction: Changes by tilting the swashplate through zero, so the pump reverses without any valve switching
• Built-in extras: Integrated charge (boost) pump, high-pressure relief valves with boost check valves, boost pressure relief valve

A4VG Series 32 Control Options

The control is where most of the model code variation lives. The most common options include:

HW: hydraulic control, proportional to pilot pressure or lever

Used where an operator moves a hydraulic pilot valve or mechanical lever. Simple and robust.

EP: electro-hydraulic proportional control

A solenoid-driven control that takes a current signal. This is the go-to choice for machines with electronic controllers and joystick or pedal inputs.

EZ: electric two-point control

Switches between two displacement settings. Common on machines that only need a crawl mode and a transport mode.

HD: hydraulic control, pressure-related

Adjusts displacement in relation to a control pressure, often used where an external signal drives pump output.

DA: speed-related hydraulic control

Designed for drives where displacement should follow engine speed, which gives a natural feel on diesel-powered machines.

Tip: Which options are offered depends on the size, so confirm availability for your displacement before specifying.

Real-World Applications and Examples

Compact wheel loader

A 56 or 71 size A4VG with EP control drives a variable motor on the axle or a transfer case. The electronic controller blends engine speed and operator demand, giving smooth inching at low speed and full tractive effort when needed.

Road roller

Steady, reversible, low-speed control is critical for finish quality. The stepless response of the A4VG lets the operator reverse the drum without jerk, and the closed circuit provides dynamic braking on slopes.

Transit mixer truck

The drum drive needs constant, controllable rotation under changing load. A series 32 pump with a through-drive can also power an auxiliary circuit from the same input shaft.

Other common uses

• Sweepers and compact municipal equipment
• Forestry and harvesting machines
• Drilling and piling rigs
• Telehandlers and special-purpose carriers
• Industrial and marine winch or propulsion drives

Maintenance and Troubleshooting

Start with the basics

1. Check boost pressure at the gauge port with the engine at working speed.
2. Inspect the charge filter and replace it on schedule.
3. Check the case drain flow. Excess drain flow signals internal wear.
4. Look at the oil: color, smell, contamination, water.

Common symptoms and likely causes

• Machine won't move or is weak in one direction: Faulty high-pressure relief valve, low boost pressure, or a control problem
• Noisy pump: Air ingress, cavitation from a blocked filter, or high viscosity on cold start
• Overheating: Worn pump or motor, poor cooling, or a stuck boost relief valve
• Sluggish response: Control orifice blockage, contaminated pilot oil, or a worn control piston

Most premature failures trace back to contamination or cavitation, not to the pump design itself.

Buying, Replacing and Cross-Referencing

When you need a replacement:

1. Read the nameplate and record the full model code and serial number
2. Confirm series: Series 32 and series 40 look similar but are not drop-in identical in every configuration. Check port plates, control interfaces and mounting dimensions.
3. Choose new, remanufactured, or repaired based on downtime cost and machine value
4. Ask for a test report on remanufactured units, covering displacement, leakage, and control response

For more information on the A4VG hydraulic pump, please visit https://www.baolilaihydraulic.com/product/.

Specifications

Selection Table

Q1: What is the difference between A4VG and A4VSO?

A1: The A4VG is designed for closed circuits with an integrated charge pump and built-in valves. The A4VSO is built for open circuits, where the pump draws from and returns to a tank.

Q2: How do I know if my A4VG is worn out?

A2: Warning signs include rising case drain flow, loss of power under load, excess heat, noise, and metal particles in the filter. A flow and pressure test on a bench or in the machine will confirm it.

Q3:How to purchase an A4VG hydraulic pump?

A3:You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.

Q4:What is the price and delivery time of the A4VG hydraulic pump?

A4:The specific price and delivery time will be provided based on the specific model you provide.