Disclosed is a gear pump including a pumping chamber in which a first shaft and a second shaft are rotated about their respective axes, each of the first and second shafts supporting at least one hydraulic-pumping element that hydraulically pumps a fluid in the pumping chamber, the at least one hydraulic-pumping element of each of the first and second shafts being positioned in the pumping chamber and each having at least one first radial projection. In the pumping chamber, each of the first and second shafts further supports at least one mechanical drive pinion that rotates each of the first and second shafts, each mechanical drive pinion having second radial projections. The at least one mechanical drive pinion is separate from the at least one hydraulic-pumping element, and the number of the at least one first radial projection and of the second radial projections is different.