99 silverado 4X4

My ABS and BRAKE light come on and go off here and there--usually when I hit bumps (often).

I've heard it may be a vehicle speed sensor on the side of the tranny or in the front wheels shorting. Any suggestions?

Thanks!

look at the steel brake line that goes across the rear diff it might be broken and leaking. does the pedal feel light?? also look for leaks at the abs pump it's located in the frame rail around the drivers door. if you don't see any leaks get it scanned. the speed sensors should only turn on the abs light the brake light means the e-brake is on or the pressure differental valve senses low pressure somewhere(leak) also check there the rear rubber lines atatch to the rear calipers this is a common leak on your truck. good luck