A planetary gear system (P) includes a sun gear (2), a ring gear (4) a carrier (6) located between the sun and ring gears (2, 4), and planet pinions (8, 10) organized in two arrays and supported on flexpin assemblies (32, 34) in the carrier (6). All of the gearing is helical, with the sun and ring gears (2, 4) having their teeth arranged in at double helix angles (herringbone) and the planet gears (8, 10) at single helix angles. The pinions (8) of the one array engage the teeth of one angle on the sun and ring gears (2, 4) and the pinions (10) of the other array engage the teeth of the other angle on the sun and ring gears (2, 4). Torque transfers through the carrier (6) through two torque paths (a, b)—one to the flexpin assemblies (32) for one array and the other to the flexpin assemblies (34) of the other array—and the paths (a) is stiffer than the path (b). Owing to the helical cut of the teeth the planet pinions (8, 10) of the two arrays exert oppositely directed axial forces (A) on the sun gear (2). The sun gear (2) is free to shift axially or float with respect to the planet pinions (8, 10) of the two arrays, so the axial forces (A) imparted to the sun gear, while opposite, are equal. Hence, the tangential forces (T), which transfer the torque, are likewise equal, notwithstanding the difference in flexibility of the two torque paths (a, b). Even though the carrier (6) may undergo different deflections at the flexpin assemblies (32, 34) for the two arrays of planet pinions (8, 10), the planet pinions (8, 10) of the two arrays transfer torques of equal magnitude.