[98SteedaGT]

Mine does the same thing if I have to slow down quikly.. I have been told is cause by slack in the gear set and it is actually the pinion and ring teeth striking each other because there's a small gap between them.... I don't know if this is the same in your case, but a rear-end shop should be able to answer that for you, other than being an obnoxious noise, I don't know if it would be damaging to the set... I would think after years of it, it may weaken some of the teeth, but I am not a mechanic...