Uses meshing gears to pump fluid. Simple, reliable, and cost-effective. Common on smaller excavators (under 2 tons). Fixed displacement - flow rate is constant at a given RPM.

Uses pistons in a rotating cylinder block with adjustable displacement. Found on premium/larger machines (1.8+ ton class). More efficient - adjusts flow based on demand, reducing fuel consumption and heat generation.

Two gear pump sections in one housing, providing separate hydraulic circuits. Common configuration noted as 'two-section hydraulic gear pump' in specifications.