The rear brakes on my 1999 chevy silverado 3500

hello fello car nuts! i have a '03 tahoe, while driving down the road the speedo needle would drop slowly to 0, i changed out the speedo sensor on the tail shaft of the tranny. in doing so this caused my brakes to go crazy. the ABS ligh comes on, the brake indicator light comes on, then the service brake alarm starts dinging, and every so often the peddle pulsates while pushing them! please help! i have tried to reset the computer by diconnecting the battery, but nothing helped..

Ummm I do not wish to step on you toes mustgo,But you must bleed the cyl.the most distance from the master cylinder first.I agree with your solution .There is one other thing.Its a brake proportioning valve.The more load in the back,the more brake.less load ,less brake.It connects onto the rear axle from the chassis and has a valve small setup from the brakes.Make sure its not damaged or bent.Its usually a thin solid metal rod.Cheers