have a look at the prop (BOTH) UJ's, use a good lamp spin em round, look for signs of rust staining, if the front prop uj is failing (common) it will show rust and the rust will run out the uj when it gets wet if you get me,

when you twisted it as described above, what you need to be sure of is that the uj moves as the prp does.. if there is play thats the problem, the rattle noise when you rock it back and forth is usual mate (though not excessive)