Bosch Rexroth A4VTG closed-circuit hydraulic pump for the Holmer agricultural equipment 1059021334 1059022817 1059028087 1059028090 3110000018

The A4VTG is a variable-displacement axial-piston pump built on a swashplate design, engineered exclusively for closed-circuit hydrostatic transmissions. In a closed circuit, hydraulic fluid flows directly between the pump and its matched motor in a continuous loop, rather than drawing from and returning to an open reservoir on every cycle. This design delivers faster response, tighter control, and higher efficiency — exactly what's needed when a heavy machine has to reverse direction, crawl at partial throttle, or hold a load without drifting.

Why Closed-Circuit Hydraulics Matter for Holmer Equipment

Holmer builds some of the most sophisticated self-propelled sugar beet harvesters and root-crop equipment on the market, and machines like the Terra Dos T4 and Terra Dos 5 rely on hydrostatic drivetrains rather than conventional mechanical transmissions. That choice isn't incidental — it's what makes the machine's advanced field behavior possible.

Hydrostatic Drives in Self-Propelled Harvesters

A hydrostatic drive built around a closed-circuit variable pump gives Holmer machines several practical advantages in the field:

Infinitely variable ground speed — the operator can creep at fractions of a kilometer per hour during precision lifting or accelerate for headland turns, all without clutching or shifting.

Instant directional response — because the pump can swing through neutral and reverse flow smoothly, the machine can change direction rapidly for maneuvering in tight rows or around obstacles.

Load-sensing power distribution — displacement can be automatically reduced as engine load rises elsewhere (for example, when the lifting or cleaning turbines demand more power), protecting the engine from stalling while keeping the machine moving.

Precision Control for Field Operations

Sugar beet harvesting punishes equipment: uneven ground, variable soil density, and the need to maintain consistent lifting depth and forward speed simultaneously. A closed-circuit axial-piston pump paired with electro-hydraulic or hydraulic-pilot control modules lets the machine's onboard electronics fine-tune propulsion in real time — which is a big part of how modern Holmer harvesters maintain harvesting quality even at high throughput.

Key Technical Characteristics

While exact figures vary by displacement size and ordering code, the A4V closed-circuit family generally shares this technical envelope:

Maintenance, Troubleshooting, and Replacement Considerations

Signs of Wear or Failure

Technicians servicing Holmer hydrostatic drives should watch for:

Loss of top speed or sluggish acceleration, often pointing to internal leakage as piston/cylinder clearances wear.

Overheating of hydraulic fluid, which can indicate a failing charge pump or degraded relief valve settings.

Erratic direction changes or hunting, suggesting control-module or pilot-pressure issues rather than the pump's rotating group itself.

Unusual noise or cavitation, frequently traced to low charge pressure, a clogged suction filter, or air ingress.

Fluid and Filtration Requirements

Closed-circuit piston pumps are unforgiving of contaminated or degraded fluid. Rexroth specifies strict cleanliness classes (per ISO 4406) for these units, and using the wrong viscosity or an out-of-spec fluid accelerates wear on the precision-machined pistons and cylinder bores. Filter cartridges with adequate beta ratios and regular fluid analysis are cheap insurance against a very expensive pump replacement.

For more brand and equipment models, please visit https://www.baolilaihydraulic.com/brand/

Q1: What's the practical difference between A4VG and A4VTG?

A1: Both are closed-circuit swashplate piston pumps sharing the same core technology. A4VG is the general-purpose mobile-machinery pump most commonly used for travel drives. A4VTG was originally developed for drum drives on concrete mixers and is also used in excavators, cranes, and similar high-pressure rotary applications. They're related but not automatically interchangeable.

Q2: How do I know if my closed-circuit pump needs to be rebuilt or replaced?

A2: Persistent loss of top speed, sluggish response, overheating fluid, or unusual noise are the classic warning signs. A hydraulic technician can pressure-test the circuit and inspect the rotating group to determine whether a rebuild (replacing pistons, valve plate, and seals) or a full unit exchange is more cost-effective.

Q3: What is the price and delivery time of the Rexroth A4VTG pump for the Holmer agricultural equipment?

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

Q4: How to purchase a Rexroth A4VTG pump for the Holmer agricultural equipment?

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