A4VG28DA + GSP2H Double Pump
1. Product Overview
This tandem double pump assembly consists of A4VG28DA variable displacement axial piston pump matched with a GSP2H external gear pump, driven by a common input shaft.
A4VG28DA is a swashplate axial piston variable pump specially designed for closed-circuit hydrostatic transmission. DA control means speed-sensitive automatic control, widely used for vehicle travel drive systems.
GSP2H gear pump serves as auxiliary pump, used for system charge oil supply, pilot control oil or cooling circuit power supply.
The tandem integrated structure saves installation space. High-quality interchange aftermarket assembly can replace original pump unit for machinery maintenance and overhaul.
Model Code Explanation
- A4VG：Series of closed-circuit axial piston pump
- 28：Theoretical displacement: 28 cc/rev
- DA：Speed-proportional automatic travel control
- GSP2H：Auxiliary external gear pump model
- Double Pump = Tandem Pump (Main piston pump + auxiliary gear pump assembly)
2. Main Technical Parameters
Item Specification
Main Pump Model A4VG28DA Variable Axial Piston Pump
Main Pump Displacement 28 cc/rev
Control Mode DA speed sensitive control
Rated Working Pressure 400 bar (40 MPa)
Peak Pressure 450 bar (45 MPa)
Auxiliary Pump Model GSP2H External Gear Pump
Auxiliary Pump Displacement: Reference GSP2H standard specification
Rotation Direction Determined according to original equipment requirement
Drive Form Tandem common shaft input
Applicable Hydraulic Oil ISO VG46 anti-wear hydraulic oil
Operating Temperature -20℃ ~ +95℃
Seal Material NBR; FKM high temperature sealing optional
3. Working Principle
The power input drives the main shaft, simultaneously driving A4VG28DA main piston pump and GSP2H auxiliary gear pump.
1. A4VG28DA Main Pump: Supplies high-pressure oil to closed-loop travel hydraulic motor. DA controller automatically adjusts pump displacement according to engine speed and load, realizing stepless speed regulation for vehicle travelling. The pump can realize forward, stop and reverse movement by changing flow direction.
2. GSP2H Gear Pump: Continuously provides charge oil for closed circuit, replenishes internal leakage of main circuit; meanwhile supplies pressure oil for pilot control loop or hydraulic cooling system.
Two pumps work independently with one power input, realizing integrated power supply for main driving circuit and auxiliary control circuit.
4. Core Advantages
1. Tandem combined design, single power input, compact layout, greatly saving installation space on mobile machinery.
2. A4VG28DA with DA speed sensing control, excellent matching performance for travel drive, stable vehicle speed regulation.
3. Main pump supports high pressure closed circuit transmission, high volumetric efficiency under continuous heavy load.
4. GSP2H gear pump features stable flow output, reliable charge oil supply to prevent closed circuit cavitation.
5. Complete interchange installation dimensions consistent with original tandem pump assembly, direct plug-and-play replacement.
6. Mature aftermarket replacement solution, shorter delivery cycle compared with original assembly.
5. Application Range
Mainly applied to small & medium wheeled machinery, road rollers, asphalt pavers, off-road vehicles, small tracked vehicles with closed-circuit hydrostatic travel system.
Function: Closed-loop travel drive + auxiliary charge/pilot oil supply.
6. Common Faults & Replacement Suggestion
Typical failures: Weak travelling power, unstable vehicle speed, high hydraulic oil temperature, abnormal pump noise, shaft seal oil leakage, insufficient charge pressure.
Fully clean hydraulic pipelines and replace filter elements before installation. Ensure hydraulic oil cleanliness to avoid impurities damaging piston assembly, valve plate and gear pair. Replace complete tandem pump assembly if internal core components suffer severe wear.
