Rexroth A8VO55 swashplate axial piston variable double pump

The A8VO55 is a variable-displacement double pump — essentially two pumps in one housing, each with its own swash angle and its own control circuit. It was designed by Bosch Rexroth for open-circuit hydrostatic drives, meaning fluid is drawn from a reservoir, pushed through the system, and returned to the tank rather than circulated in a closed loop.

The "55" in the name refers to the geometric displacement per revolution (roughly 55 cc/rev per pump section), which sits at the small end of the A8VO lineup that also includes the A8VO80, A8VO107, A8VO140, A8VO160, A8VO200, and A8VO225.

How the Variable Displacement Mechanism Works

Unlike a bent-axis piston pump, where the entire cylinder block tilts relative to the drive shaft, the A8VO55 uses the more common swashplate arrangement: the shaft and cylinder block stay in line, and a separate plate tilts to change piston stroke. A servo piston, driven by the control valve, pushes the swashplate to the commanded angle.

Control options generally fall into a few families:

Pressure-compensated (LR) control — holds a set pressure by reducing displacement as pressure rises

Power control (LR3 or similar) — limits combined power draw of both circuits so the engine isn't overloaded

Electro-hydraulic proportional control — lets an onboard controller command swash angle directly, useful for machines with electronic load-sensing

For most mobile equipment applications, the A8VO55 runs a power controller that automatically de-strokes one or both circuits when total demand exceeds the engine's available power — a practical way to prevent stalling under combined load.

Key Features and Advantages

Dual-Circuit Independent Control

Because each rotating group has its own swashplate and can be regulated separately, one circuit — say, the drive wheels — can run at full flow while the other — say, an auger or mixer drum — runs at reduced flow, all from a single pump body sharing one input shaft. This is the main reason double pumps like the A8VO55 show up so often on self-propelled machines with a working function and a travel function.

Integrated Auxiliary Pump

The built-in charge/auxiliary pump supplies pilot pressure for the control system and boost pressure to keep the main circuits from cavitating. It typically includes its own pressure-relief valve and, in some configurations, an additional pressure-reduction valve for sensitive pilot circuits.

Direct Engine Mounting

The A8VO55 is built to bolt directly onto a diesel engine's flywheel housing, eliminating the driveshaft, coupling, and separate mounting bracket that a remote-mounted pump would need. This keeps the installation compact and reduces one more source of misalignment and vibration.

Power Take-Off for Additional Pumps

A through-drive on the back of the unit allows a second axial piston or gear pump to be stacked behind the A8VO55, which is common on machines that need a third circuit (steering, cooling fan, or an implement function) without adding a second engine PTO.

Common Applications

The A8VO55 and its siblings show up wherever a machine needs strong, independently controlled hydrostatic drive and work functions from one engine.

Concrete Mixer and Pump Trucks

The travel circuit drives the wheels while the second circuit runs the drum or the concrete pumping mechanism, letting the operator mix or pump while stationary and drive separately without cross-talk between the two functions.

Rotary Drilling and Boring Rigs

One circuit drives travel/tracks, the other powers the rotary head or auger — both needing precise, independent flow control since drilling torque demands change constantly.

Asphalt Pavers

Independent left/right or drive/auger circuits benefit from the same dual, isolated control the A8VO55 provides, helping keep paving speed and material feed rate stable even as ground conditions change.

Cranes and Material Handlers

Travel and slew/winch functions are frequently split across the two pump sections so that boom or winch operation doesn't rob flow from propel, or vice versa.

For more information on the A8VO55 hydraulic pump, please visit https://www.baolilaihydraulic.com/product/.

Specifications

Selection Table

Q1: What's the difference between Series 61 and Series 63 units?

A1: They're different generations of the design with some differences in control valve fitment and internal detail. Spare parts and control components should be matched to the series stamped on the nameplate, not assumed interchangeable across series.

Q2: Is the A8VO55 a closed-circuit or open-circuit pump?

A2: Open circuit. It draws fluid from a reservoir and returns it to the tank, as opposed to closed-circuit pumps used in dedicated hydrostatic transmissions where fluid recirculates between pump and motor.

Q3: How to purchase an A8VO55 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 A8VO55 hydraulic pump?

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