Brakes and transmission

1991 chevy suburban 3/4 ton engine 350 5.7 liter my brakes pedal gets hard then pops and I have to push real hard to stop, also when I take off again it shifts hard and some times down shifts then up, down, and sometimes the brake warning light comes on, which seems to make the shifting and slipping worse. Could the two problems be related or could one cause the other?Now the brake warning light comes on always and tranny slips and shifts hard up and down PS. The torque converter clutch was rebuilt two years ago