Sue fordgt

Hi I need some advice I own 2003 ba gt.83, 000 km Knocking noise or sounds like something loose Got centre bearing and rear bushes all replaced as car felt like it was floating at rear. After replacing rear bushes still have sound at rear driving me nuts. Spoke to mechanic says when new bushes go in something you can hear think s probably there before new bushes. The problem wasnt yhere before new bushes but now sound ay the rear. Any opinions please