I have a three wheeled vehicle in a tricycle configuration attached to a fixed frame. Each wheel is powered by an AC electric motor. The AC motors are fed by motor controllers that take a speed demand. The single main wheel (which is also steerable) has a lower gear ratio than the rear wheels so it has a theoretical higher top speed. 

When the vehicle drives in a straight line each of the motor controllers are given identical speed requests. Unfortunately feedback from the controller indicates that some motors are pushing while some are pulling. In particular we have a common scenario where one rear wheel is pushing while the front wheel is trying to slow down. The third wheel will often have almost no current. 

What can be done to make all three motors work together and avoid situations where they fight? Is there a way to change the request to the motor controller to encourage the drives to work together? Do we have to switch from a speed request setup to a current control setup? If so what is the appropriate way to control the motors then? 

Let me know if I haven't included any important details and I will update my question.