My 2002 BA Falcon makes a metallic knocking noise on takeoff, which disappears at about 15k.p.h. It sounds like a loose universal joint, but I checked them and they're all o.k. I jacked a wheel up and turned the wheel back and forth. The noise seems to be coming from inside the diff, which is a independent suspension type. I checked the oil in It and It's full. Any Ideas on the cause of the noise and how to fix It? Cheers.

Did you check the centre bearing in the tailshaft?