On my TA01 Escort, fully ballraced and greased, when I spin one of the front wheels by hand, the opposite wheel spins in the opposite direction beautifully - for 2-3 seconds. It appears friction free. However when I spin one of the rear wheels, the opposite one spins in the opposite direction but both rear wheels stop instantly when I let go. Should the rear diff spin as freely as the front one when not engaging the motor?