A split torque gearbox comprising: a first compound gear comprising: a first piston assembly comprising: a first piston housing comprising a first fluid inlet; and a first piston coupled to a first driveshaft, the first piston received in the first piston housing and defining a space within the first piston housing exposed to the first fluid inlet, wherein the first driveshaft is secured via a first bearing (312a; 314a), the first bearing (312a; 314a) preventing radial movement of the first driveshaft and permitting axial movement of the first driveshaft; a second compound gear comprising: a second piston assembly comprising: a second piston housing comprising a second fluid inlet; and a second piston coupled to a second driveshaft, the second piston received in the second piston housing and defining a space within the second piston housing exposed to the second fluid inlet, wherein the second driveshaft is secured via a second bearing (312b; 314b), the second bearing (312b; 314b) preventing radial movement of the second driveshaft and permitting axial movement of the second driveshaft; and a fluid line coupled to the first fluid inlet to supply a fluid to the first piston assembly at a predetermined pressure, the fluid line coupled to the second fluid inlet to supply fluid to the second piston assembly at the predetermined pressure; wherein an effective area of the first piston is larger than a cross-sectional area of the first driveshaft, and an effective area of the second piston is larger than a cross-sectional area of the second driveshaft. a first compound gear comprising: a first piston assembly comprising: a first piston housing comprising a first fluid inlet; and a first piston coupled to a first driveshaft, the first piston received in the first piston housing and defining a space within the first piston housing exposed to the first fluid inlet, wherein the first driveshaft is secured via a first bearing (312a; 314a), the first bearing (312a; 314a) preventing radial movement of the first driveshaft and permitting axial movement of the first driveshaft; a first piston housing comprising a first fluid inlet; and a first piston coupled to a first driveshaft, the first piston received in the first piston housing and defining a space within the first piston housing exposed to the first fluid inlet, wherein the first driveshaft is secured via a first bearing (312a; 314a), the first bearing (312a; 314a) preventing radial movement of the first driveshaft and permitting axial movement of the first driveshaft; a second compound gear comprising: a second piston assembly comprising: a second piston housing comprising a second fluid inlet; and a second piston coupled to a second driveshaft, the second piston received in the second piston housing and defining a space within the second piston housing exposed to the second fluid inlet, wherein the second driveshaft is secured via a second bearing (312b; 314b), the second bearing (312b; 314b) preventing radial movement of the second driveshaft and permitting axial movement of the second driveshaft; and a second piston housing comprising a second fluid inlet; and a second piston coupled to a second driveshaft, the second piston received in the second piston housing and defining a space within the second piston housing exposed to the second fluid inlet, wherein the second driveshaft is secured via a second bearing (312b; 314b), the second bearing (312b; 314b) preventing radial movement of the second driveshaft and permitting axial movement of the second driveshaft; and a fluid line coupled to the first fluid inlet to supply a fluid to the first piston assembly at a predetermined pressure, the fluid line coupled to the second fluid inlet to supply fluid to the second piston assembly at the predetermined pressure; wherein an effective area of the first piston is larger than a cross-sectional area of the first driveshaft, and an effective area of the second piston is larger than a cross-sectional area of the second driveshaft.