I drive a 2002 GMC 1500hd with 96,000 miles on it. At lower speeds, my truck seems like it activates the abs system early and causes the pedal to jump. While the pedal jumps you can hear a whining noise.The problem causes my braking distance to diminish significantly. Please help.

If this is occuring at speeds of less than about 5 to 10 mph or during slow speed parking lot types of manuvers then the problem may be due to an ABS sensor at one of the front wheels. The sensor develops a very small build up of corrosion beneath it which pushes it away from the sensor tone ring just enough for the signal to degrade and for the ABS to think the wheel is locked up which, in turn, activates the ABS system which, in turn again, gives you the pedal jump and can extend the braking distance. When I find this type of problem I usually replace both of the front wheel sensors and clean up the mounting surface to fix this problem. Sometimes the problem can be seen using a scan tool that shows the actual readings the sensors are producing but many scan tools aren't quick enough to catch that data.