What does the damper axle do and do you have to keep them on the car?The reason I ask is after they installed the new control arms I noticed they left them off.

 

when you install new upper/lower control arms, it makes the quad shock/axle damper/transverse shock practically useless. A lot of mustang guys take them off or reverse them to fit bigger tires in the rear. It's mainly an axle locating thing, which is cured more by the control arms.