1982 GMC C3500 brakes

There can be lots of reasons and the system needs to be troubleshooted to isolate the source of the problem. It could be the master cylinder, pushrod adjustment, frozen calipers or any of the flex hoses.

Thank you, ill check all that

There is a systematic way of doing that. You aren't going to find anything visually. You have to wait until they are locked up, determine which wheels are locked up and then start at the master cracking lines open and working toward the wheel until the wheel suddenly free up.