An electro-hydraulic high-pressure oilfield pumping system, comprising: a fracturing (frac) pump configured to pressurize a frac fluid for delivery into a well that extends into a subterranean geological formation; a primary electric motor that has a motor shaft and defines a prime mover of the electro-hydraulic high-pressure oilfield pumping system; a transmission with multiple ranges that provide multiple drive ratios, the transmission arranged between and configured to deliver power from primary electric motor to the frac pump; a hydraulic starting motor selectively delivering power through the transmission to rotate the motor shaft of the primary electric motor; a slow frac hydraulic motor selectively delivering power through the transmission to rotate the motor shaft of the primary electric motor; a hydraulic power pack configured to selectively permit or prevent flow of hydraulic fluid to each of the hydraulic starting motor and the slow frac hydraulic motor for activating or deactivating the hydraulic starting motor and the slow frac hydraulic motor, wherein the system defines: a primary electric motor starting mode in which the hydraulic starting motor delivers power through the transmission to rotate the motor shaft of the primary electric motor to a first speed that corresponds to a fixed rated speed of the primary electric motor; a slow frac mode in which the slow frac hydraulic motor delivers power through the transmission to rotate the motor shaft of the primary electric motor to a second speed that is less than the fixed rated speed of the primary electric motor; and a frac mode in which the primary electric motor is energized and delivers power through the transmission and to the frac pump. a fracturing (frac) pump configured to pressurize a frac fluid for delivery into a well that extends into a subterranean geological formation; a primary electric motor that has a motor shaft and defines a prime mover of the electro-hydraulic high-pressure oilfield pumping system; a transmission with multiple ranges that provide multiple drive ratios, the transmission arranged between and configured to deliver power from primary electric motor to the frac pump; a hydraulic starting motor selectively delivering power through the transmission to rotate the motor shaft of the primary electric motor; a slow frac hydraulic motor selectively delivering power through the transmission to rotate the motor shaft of the primary electric motor; a hydraulic power pack configured to selectively permit or prevent flow of hydraulic fluid to each of the hydraulic starting motor and the slow frac hydraulic motor for activating or deactivating the hydraulic starting motor and the slow frac hydraulic motor, a slow frac hydraulic motor selectively delivering power through the transmission to rotate the motor shaft of the primary electric motor; a hydraulic power pack configured to selectively permit or prevent flow of hydraulic fluid to each of the hydraulic starting motor and the slow frac hydraulic motor for activating or deactivating the hydraulic starting motor and the slow frac hydraulic motor, wherein the system defines: a primary electric motor starting mode in which the hydraulic starting motor delivers power through the transmission to rotate the motor shaft of the primary electric motor to a first speed that corresponds to a fixed rated speed of the primary electric motor; a slow frac mode in which the slow frac hydraulic motor delivers power through the transmission to rotate the motor shaft of the primary electric motor to a second speed that is less than the fixed rated speed of the primary electric motor; and a frac mode in which the primary electric motor is energized and delivers power through the transmission and to the frac pump. a primary electric motor starting mode in which the hydraulic starting motor delivers power through the transmission to rotate the motor shaft of the primary electric motor to a first speed that corresponds to a fixed rated speed of the primary electric motor; a slow frac mode in which the slow frac hydraulic motor delivers power through the transmission to rotate the motor shaft of the primary electric motor to a second speed that is less than the fixed rated speed of the primary electric motor; and a frac mode in which the primary electric motor is energized and delivers power through the transmission and to the frac pump.