Bosch Rexroth A4VG closed-circuit hydraulic pump for the Ponsse Engineering Equipment 0064469 0042181

The A4VG is a variable-displacement axial piston pump of swashplate design, built for hydrostatic transmissions in a closed circuit. Its flow is proportional to drive speed and displacement, and it can be varied infinitely from zero to maximum as the swashplate swivels.

Why Closed-Circuit Pumps Suit Forest Machines

Traction under changing load

A forwarder's drive sees sudden torque demands. A hydrostatic drive delivers full tractive effort from a standstill and lets the operator feather speed continuously, without a gearbox or clutch. Because the pump can also brake the machine by acting as a hydraulic retarder, the engine and transmission take some of the downhill load.

One pump, several jobs

The through drive is an underrated feature on a forest machine. A second pump mounted on the back can feed a steering, cooling fan, or auxiliary circuit off the same engine PTO, which saves space in a tight engine bay.

Control Options You Will Meet

The suffix after the displacement tells you how the pump is controlled.

HW / HD are hydraulic controls, often used where a pilot valve or joystick pressure commands the swashplate.

DA is a speed-related hydraulic control. Pump output follows engine rpm, which gives an automotive-style feel where the machine speeds up as the operator raises engine speed.

EP is electroproportional control. One listed unit uses electric proportional control with an integrated boost pump. This is the natural choice where a machine controller manages drive behavior, anti-stall logic, or traction control.

On a modern forwarder with electronic drive management, expect EP-type control. On simpler or older machines, DA is common.

Real-World Symptoms and What They Usually Mean

Machine creeps when the lever is in neutral

Check the neutral setting on the control first, and for EP control check the electrical signal offset. It is rarely a mechanical fault on the first pass.

Loses power when hot

A worn rotating group leaks more internally as oil thins, and casedrain flow climbs. Measuring casedrain flow at operating temperature is one of the best diagnostic checks on a closedcircuit pump.

Weak or unstable drive, noise, foaming

Suspect low boost pressure or inlet restriction. Look at the boost relief valve, the boost pump, and a clogged suction or charge filter. Boost pressure in these pumps is typically in the neighborhood of 20 bar, but confirm the exact value for your model.

Overheating

Closed loops depend on the tank and cooler to shed heat through the flushing and boost circuit. Restricted or dirty coolers, and machines working hard on steep climbs, lead to heat problems. In forestry, packed sawdust and needles in coolers are a very common culprit.

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Q1: Does Ponsse use the A4VG?

A1: That depends on the model and production year. Confirm with Ponsse's parts documentation or a dealer using your machine's serial number rather than relying on general information.

Q2: Can I repair an A4VG, or should I replace it?

A2: Many rotating-group and valve components can be serviced by qualified hydraulic shops. Whether a repair makes sense depends on the damage, how long the machine has run, and whether debris has spread through the circuit.

Q3: What is the price and delivery time of the A4VG hydraulic pump for the Ponsse Engineering Equipment?

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

Q4: How do I purchase an A4VG hydraulic pump for the Ponsse Engineering Equipment?

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