Ford Repair: Rear Antilock break light, speed sensors, fist time

Question
When I break for the fist time on a "trip" my  breaks slam my 91 Bronco (5.8L) to a screetching (from the tires on the concret)halt and the body of the car tips forward. This usally happens when I haven't gone faster yet, for example comeing out of a parking lot or driveway. One I have driven for a while at  a faster speed there are no more problems. This morning when I started my car the Rear antilock light came on and didn't turn off again. I put my parking break on since I have to park at a slight incline and I always make sure I remember to release it before I go. What is/might be the problem and will it be expensive to fix?
Thanks for your time.
Jeanette

Answer
Besides just throwing parts at it you will need to have the ABS codes read.However, it is probably a sensor and the price on them is not too bad.You have a left and right rear ABS wheel sensor at about $29 a piece.You also have an couple of ABS speed sensors.One is in the tranny and one in the rear end.Hope this helps.