In at least one embodiment, a vehicle powertrain includes an engine and an electric machine mechanically coupled by a clutch. The powertrain also includes a torque converter configured to fluidly couple the electric machine to an output shaft. A controller is programmed to command a rotational speed output of the electric machine to the torque converter based on a predicted torque delivered across the clutch. The controller is further programmed to modify the command based on a difference between the commanded rotational speed output and an actual rotational speed output of the electric machine.