Auto Parts: Brakes on Cavalier, speed sensors, wheel speed

Question
Hello,
I was writing to you because I had read a question you had posted about your daughters cavalier. I was wondering if you could tell me if you were able to fix it because I also have a 2000 Cavalier with the same problem and have paid various mecanics after my father wasnt able to fix it and no one has been able to get what is wrong... My car is doing exactly the same thing... you brake, it dives or "falls" back and locks the back tires. What did you??? Please let me know I am desperate to fix the car because it is terrible in the rain. Hope to hear from you...
Thanks,
Vanessa  

Answer
    Well, first, I think you've got the wrong guy.  But I am an auto parts professional for 30 years, so...

    It is obvious that your anti-lock brakes ain't anti-locking.  The anti-lock system used as standard equipment on the Cavalier is a simplified and inexpensive version of those used on more expensive cars.  That is how they can afford to offer it as standard equipment on their cheapest car, which is good.  The bad part is that diagnosis and repair are a little tricky.  One of the inputs that the system uses is rear ride height.  When the brakes are applied and the front goes down (which is normal), the rear goes up.  The system should then release pressure to the rear wheels.  Yours isn't doing that.  There are several valves that regulate this pressure, as well as sensors.  It doesn't operate off of wheel-speed sensors like the better systems do.  Honestly, my advice is to find a mechanic who knows these systems (the dealer if necessary) and turn it over to him.  The conditions you describe are dangerous, and are going to result in an interstate spin-out eventually.