During the last week I started to hear a small chattering noise coming from the transmission area.It only would come when the truck was pulling hard at speed,example is if I was crusising at 65 mph then hit a hill or a strong gust of wind would come.If I then gave it some more thrittle I would hear the noise,when I ease up it gores away.Today I decided to lube the throw out bearing and when I did I noticed it was slightly loose.I think this is what is causing the noise. Question,is it likely to completely fail,or is this normal, and can it be tightened.The transmission is a Fuller Eaton 6 speed with 760K on it.Weave have you or anyone else experienced this??