A4VG Series Rotary Groups and Closed Circuit Pump Parts
A4VG closed circuit rotary groups and spare parts in sizes 28 to 500 for self propelled machine drive circuits, supplied as matched sets.
Product Overview
A4VG is the closed circuit variable pump that drives the wheels or tracks of self propelled machines. Because it works with a charge pump and a hot oil shuttle, wear shows up first as a loss of drive speed on a slope or a machine that creeps when the joystick is at neutral. We build the rotary group, cylinder block, piston shoes, valve plate, bearing seats and seal kits for sizes 28 through 500.
| A4VG | 28 40 45 56 71 90 125 180 250 355 500 |
|---|
Key Benefits
- Supplied as a matched set so the block, shoes and valve plate run in together
- Same envelope and spline as the original, so the pump goes back on the machine unchanged
- Available for frames the original maker has moved off its list
- Twelve month warranty on the same terms as a new original part
Application Scenarios
- Wheel loaders, rollers and pavers with hydrostatic drive
- Self propelled harvesters and sprayers
- Concrete pumps and mobile plant with a hydrostatic transmission
- Municipal and airport vehicles with hydraulic drive
Who It Is For
- Pump rebuild shops working to a customer deadline
- Plant and fleet maintenance teams
- Distributors carrying rotary group stock for local machines
- Machine builders needing a second source
Problems It Solves
- The machine has lost drive speed on gradients
- Drive creeps at neutral because the swash plate control is worn
- The pump has run hot and the charge circuit is no longer holding pressure
- The rotary group is quoted with a lead time that keeps the machine parked
Technical Features
- Cylinder block with sintered bronze running face bonded and machined after sintering
- Piston and shoe assemblies swaged and checked for shoe clearance
- Valve plate lapped to a mirror finish so the pair seals under pressure
- Retainer plate and ball guide matched to the block
- Splines and bearing seats ground after heat treatment
Specifications
Performance figures depend on the exact variant, so we confirm them against your model code rather than publishing a number that may not apply to your pump.
| Set contents | Cylinder block, pistons with shoes, retainer plate, ball guide, valve plate and spring set |
|---|---|
| Matching | Parts lapped and matched as one running set |
| Spline | To the original pattern, checked over pins |
| Marking | Neutral or your own part number on request |
| Packing | Oiled and vacuum sealed, boxed per set |
| Performance data | Confirmed against the full model code on your unit before quotation |
Materials
| Cylinder blocks | Case hardening steel with a sintered bronze running face, bonded and machined after sintering |
|---|---|
| Pistons and shoes | Case hardening steel with a bronze shoe face, swaged and hydrostatically balanced |
| Valve plates | Bearing steel or bronze faced steel depending on the frame, lapped to a mirror finish |
| Drive shafts | Alloy steel, carburised and hardened on the spline and bearing seats, ground on centres |
| Vanes and rotors | High speed tool steel and case hardening steel, hardened and ground on all working faces |
| Cam rings | Bearing quality alloy steel, through hardened then profile ground |
| Seals | Nitrile as standard, fluorocarbon or polyurethane on request for hot or fire resistant fluid duty |
Manufacturing Process
- Turning and millingBlanks are turned and milled from certified bar and forging stock on CNC machines.
- Heat treatmentCarburising, quenching, tempering or nitriding to the route the original part uses.
- GrindingBores, spline seats and running faces are ground after heat treatment so distortion is removed.
- Lapping and superfinishingValve plates, shoe faces and block faces are lapped so the pair seals under pressure.
- InspectionDimensions, hardness and surface finish are recorded against the drawing on a sampling plan.
- Assembly and testComplete pumps are built, run in and tested for efficiency, leakage and noise before packing.
Quality Control
- Incoming material certificates are checked against the grade called for on the drawing.
- Hardness is measured after heat treatment on every batch and recorded on the batch card.
- Critical bores and running faces are gauged against the drawing tolerance, not against a sample part.
- Mating parts are matched as a set so the block, shoes and valve plate run in together.
- Rebuilt pumps are bench tested for volumetric efficiency, external leakage and sound level.
- Parts are cleaned, oiled and vacuum sealed so they arrive without surface rust.
Certifications and Documentation
Supplied on request with an order. We do not claim approvals we cannot evidence.
| Material certificate | Mill certificate for the steel grade used in the batch |
|---|---|
| Hardness report | Surface and core hardness readings after heat treatment |
| Dimensional report | Measured values for the critical features named on the drawing |
| Test bench report | Flow, efficiency, leakage and sound readings for a rebuilt pump |
| Packing list and photographs | Carton contents and photographs of the packed goods before shipment |
Customization Options
- Shaft and splineKeyed, straight or splined shaft ends built to your sample or drawing.
- Port and mountingFlange, thread and mounting pattern matched to the pump already on the machine.
- Seal materialNitrile, fluorocarbon or polyurethane for hot oil, fire resistant fluid or low temperature duty.
- Rotation and displacementLeft or right hand rotation and the displacement code your circuit was set up for.
- Marking and packingNeutral packing, your own carton artwork and your own part number laser marked on the part.
Comparison With Other Products
| Point | A4VG | A4VSO | A11VO |
|---|---|---|---|
| Circuit | Closed circuit with charge pump | Open circuit | Open circuit |
| Typical duty | Hydrostatic drive | Industrial power unit | Heavy mobile work function |
| Sizes we build | 28 to 500 | 28 to 500 | 35 to 500 |
| Common symptom of wear | Loss of drive speed | Loss of pressure and flow | Slow work function under load |
Use Guide
- Record the full model code and the serial plate before stripping the unit.
- Measure the housing bore and bearing seats. A worn housing will kill a new rotary group.
- Fit the set complete rather than mixing new and used running faces.
- Renew the seal kit and the shaft bearing at the same time.
- Flush the circuit, prime the case with clean oil and run in at low pressure.
Product Photographs
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Frequently Asked Questions
Why has my machine lost drive speed on a hill?
Usually the rotary group and charge circuit together. Measure charge pressure first, then strip and inspect the block face and shoes.
Do you supply the seal kit with the rotary group?
Seal kits are a separate item and we recommend adding one with every rotary group.
Can I fit an A4VG block into an A4VSO pump?
No. The two frames are different and the parts are not interchangeable.
Do you machine the swash plate and bearing seat?
Yes. Swash plates, cradle bearings, bearing seats and control parts are all available.
Which sizes do you keep in stock?
The 56, 71, 90 and 125 sizes are the most common. Ask before ordering and we will confirm stock.
Send Us the Model Code and We Will Quote
Tell us the model code stamped on the pump, the quantity and your delivery port. A quotation with lead time usually comes back within one working day.