Rexroth A4VG variable hydraulic pump for the JCB wheel loader 20/925291 20/925347 20/925572 20/925712 20/925778 20/925380 20/925496

The A4VG is a swashplate-type axial piston pump built by Bosch Rexroth, a German manufacturer that's been a dominant force in industrial and mobile hydraulics for decades. It's designed specifically for closed-circuit hydrostatic drives — the kind of transmission you find in wheel loaders, skid steers, and other machines that need smooth, stepless speed control rather than a traditional geared powertrain.

Unlike a fixed-displacement pump, which pushes a constant volume of oil per revolution, the A4VG is variable displacement. The angle of its internal swashplate can be adjusted on the fly, which changes how much hydraulic fluid it delivers with every shaft rotation. That single design feature is what lets a wheel loader change travel speed and direction without a mechanical gearbox doing the work.

Why JCB Wheel Loaders Use the A4VG

JCB, like most major loader manufacturers, moved toward hydrostatic drivetrains on many models because they solve problems that traditional torque-converter transmissions struggle with: precise low-speed control, smoother directional changes, and better matching of power delivery to the load.

Closed-Loop Hydrostatic Transmission

The A4VG operates in a closed hydraulic circuit, meaning oil flows in a continuous loop between the pump and the drive motor rather than returning to a tank after every cycle. This keeps response times fast and allows for regenerative braking effects when the machine decelerates — the motor briefly acts like a pump, and energy gets recirculated rather than wasted.

Variable Displacement Control

Because the swashplate angle is adjustable, the operator (or the machine's electronic control unit) can command anything from zero flow to maximum flow in either direction, without touching engine RPM. This is what gives JCB loaders their characteristic smooth creep control when working a pile, and their strong, direct response when the operator wants to move fast between load and dump zones.

Key Technical Features of the A4VG Series

Swashplate Design and Displacement Range

The A4VG is available across a range of displacement sizes (commonly denoted by numbers like A4VG28, A4VG40, A4VG56, A4VG71, and up), and JCB selects the size that matches the loader model's power class and axle torque requirements. Larger loaders in the JCB range typically pair with larger-displacement A4VG units to move sufficient oil volume for their bigger drive motors and tires.

Electrohydraulic Control Options (DA, EP, HW)

Rexroth builds the A4VG with several control head options:

DA (electrohydraulic proportional control) — common on modern JCB loaders, allowing the machine's ECU to precisely manage swashplate angle based on inputs like throttle position, travel direction lever, and load sensing.

HW (hydraulic control) — a more mechanical, direct-actuation approach used on some models.

EP (electric proportional) — offers finer digital control, often paired with advanced traction management systems.

Most current-generation JCB wheel loaders lean on DA-type control because it integrates cleanly with the machine's broader electronic control architecture, enabling features like automatic declutching on braking and programmable drive modes.

Integrated High-Pressure Relief and Charge Pump

Every A4VG unit includes a built-in charge pump that keeps the closed loop topped up with makeup oil, compensating for internal leakage and preventing cavitation. High-pressure relief valves protect the circuit from shock loads — critical in a wheel loader that's constantly slamming into stockpiles and reversing under load.

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Q1: Can the A4VG pump be repaired, or does it need full replacement?

A1: In most cases, it can be rebuilt. Specialist hydraulic repair shops can replace piston shoes, the cylinder block, bearings, and seals, and recalibrate the control head. Full replacement is usually reserved for cases with severe housing damage or when a rebuild isn't cost-effective relative to a reman unit's price.

Q2: How long does an A4VG pump typically last in a JCB wheel loader?

A2: There's no fixed number — it depends heavily on duty cycle, oil cleanliness, and maintenance discipline. Well-maintained units in moderate-duty applications can run well past 8,000-10,000 hours, while machines in abrasive, high-contamination environments (demolition, scrap handling) may see wear much sooner.

Q3: What is the price and delivery time of the A4VG hydraulic pump for the JCB wheel loader?

A3: The specific price and delivery time will depend on the equipment model or specific product model you provide.

Q4: How to purchase an A4VG hydraulic pump for the JCB wheel loader?

A4: You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.