I have a 92 camaro rs with front disc and rear drum. I havent done anything lately except put some clean brake fluid in there. They locked up coming up to a stopsign for no apparant reason and then today when it was raining they locked up and I didnt even use any force. I slid about 25ft thanks to an open turn lane I didnt hit anybody. Well I just purchased both new front calipers,stainless steel lines and cross drilled rotors. The backs and just getting the basic. I bought aluminum drums and will get new shoes. Do I need to buy a new brake booster along with proprtional valve?

 

You need to take a close look at the rear wheel cylinders and the axles seals. Make sure their not leaking since this can cause the exact problem you are having. I would think that you wouldn't need a booster since a booster will cause a hard pedal not a grabby one. Look like you need to do a complete brake inspection then go from there.