A transmission assembly , comprising: a ring gear configured to receive an input torque from a power source ; a carrier assembly coupled to the ring gear , the carrier assembly configured to rotate about a first axis and comprising: a housing ; and a spider gear rotatably coupled to the housing ; a carrier outlet shaft comprising a carrier outlet gear in meshed engagement with the spider gear , wherein the carrier outlet shaft is configured to transmit an output torque to a driveshaft ; a control shaft comprising a control gear in meshed engagement with the spider gear ; and a load applicator coupled to the control shaft , wherein the load applicator is configured to provide a resistive torque to the control shaft to resist rotation of the control shaft and vary a gear ratio between the driveshaft and an input shaft ; a torque applicator configured to controllably apply torque to the carrier outlet shaft ; a hydraulic circuit coupled to the load applicator and to a load controller configured to control the amount of resistive torque applied to the control shaft from the load applicator ; wherein the load applicator comprises a pump fluidly coupled to the hydraulic circuit ; wherein the torque applicator comprises a motor fluidly coupled to the hydraulic circuit and is configured to convert pressure of hydraulic fluid in the hydraulic circuit into rotational torque; characterised in that the transmission assembly further includes: a bypass circuit fluidly coupled to the hydraulic circuit ; and a bypass valve fluidly coupled to the bypass circuit and configured to permit a fluid flow in the hydraulic circuit to bypass the torque applicator when the bypass valve is in an open position. a ring gear configured to receive an input torque from a power source ; a carrier assembly coupled to the ring gear , the carrier assembly configured to rotate about a first axis and comprising: a housing ; and a spider gear rotatably coupled to the housing ; a housing ; and a spider gear rotatably coupled to the housing ; a carrier outlet shaft comprising a carrier outlet gear in meshed engagement with the spider gear , wherein the carrier outlet shaft is configured to transmit an output torque to a driveshaft ; a control shaft comprising a control gear in meshed engagement with the spider gear ; and a load applicator coupled to the control shaft , wherein the load applicator is configured to provide a resistive torque to the control shaft to resist rotation of the control shaft and vary a gear ratio between the driveshaft and an input shaft ; a torque applicator configured to controllably apply torque to the carrier outlet shaft ; a hydraulic circuit coupled to the load applicator and to a load controller configured to control the amount of resistive torque applied to the control shaft from the load applicator ; wherein the load applicator comprises a pump fluidly coupled to the hydraulic circuit ; wherein the torque applicator comprises a motor fluidly coupled to the hydraulic circuit and is configured to convert pressure of hydraulic fluid in the hydraulic circuit into rotational torque; characterised in that the transmission assembly further includes: a bypass circuit fluidly coupled to the hydraulic circuit ; and a bypass valve fluidly coupled to the bypass circuit and configured to permit a fluid flow in the hydraulic circuit to bypass the torque applicator when the bypass valve is in an open position. a bypass circuit fluidly coupled to the hydraulic circuit ; and a bypass valve fluidly coupled to the bypass circuit and configured to permit a fluid flow in the hydraulic circuit to bypass the torque applicator when the bypass valve is in an open position. <EOS>