Angular momentum is conserved, which means that the change in angular momentum of object A must be exactly canceled by the change in angular momentum of the object exerting a torque on object A. So, the objects, A and B, exert equal and opposite torques on each other. But, the contact forces between the objects must also be equal (Newton's 3rd). Torque= F x r, so what if the moment arm (r) of object A is larger than object B? If torques are equal and forces are equal, moment arms must also be equal, but this is certainly not always the case. What's going on?