Sound like your guibo. Have the car jacked up, shut the engine down, and rotate the centre shaft back and forth with your hands. If there is alot of free play, that confirms it.....hm actually that would be the universal joint and not the guibo I believe. Look at the guibo visually. It may be obviously worn and damaged as well.
If your U joints are screwed, please purchase a rebuilt one. A good used one can be purchased from the yard if you know how to inspect it. Replacing the centre shaft is not a simple task so it might not be advisable if cutting corners only means you'll need to do the work once again down the line.