Air Brake Antilock problems of the 1996 Ford Windstar

We have been having our abs light come on when the van travel on the highway. When traveling at speeds between 50-55 after 3-10 miles at this speed the abs light comes on. This problem started in Dec 1998 and the dealership thought they fixed the problem by cleaning the sensors. The problem kept coming back . Now we were informed that there is a toothed collar on the front axles that the sensors monitor for speed. These rings crack and the sensor picks up the crack. The dealership replaced the left front axles on the van on 24 sept 1999. They figured this would fix the problem. We drove the van to my parents home in scranton, PA and 7 miles into the journey the abs came on again. The problem will not go away and Ford has no spare parts to replace these rings until 15 oct. How can someone place a 5 star government safety rating on a vehicle when the main safety does not operate. Within the last 3 months this van has had the subframe mount, steering rods and part and last the whole left axle. If we keep this up my wife will have a whole new van. We have a handicapped child and the van is very useful for him and his baby brother. We don't drive it but local any more. We don't feel safe. We are asking how this van received a 5 star safety rating and what could you do to help us get this problem corrected. We only buy american made cars, but as of latley I am looking at old junk cars. Please feel free to contact us at anytime to talk about this. Thank you for you time.

In cold snowy weather when appying the abs brakes, they failed three times, causing an accident, took to dealer, couldn't find problem .