A system and method for controlling a powertrain of a vehicle having an engine configured to output a variable torque, can include a transmission with a plurality of gear ratios and selectively driven by the variable torque, and a pair of wheels selectively driven by the transmission. The system can include a longitudinal acceleration sensor and a controller. The controller can be in electrical communication with the longitudinal acceleration sensor. The controller can be configured to determine an inertial value of the vehicle based on data from the longitudinal acceleration sensor prior to a shift from one of the plurality of gear ratios to another of the plurality of gear ratios. The controller can also be configured to determine a first estimate of a real-time torque value based on at least one of an engine map, the plurality of gear ratios, a torque converter map and driveline losses, and to determine a second estimate of a real-time torque value based on the inertial value and data from the longitudinal acceleration sensor, during the shift from the one of the plurality of gear ratios to the another of the plurality of gear ratios.