JACornell

I just bought my 1st 4th gen ta 98 ls1 a4 with 172k, not sure if anything has ever been done to it or how long it has sat before I bought it. Under normal city conditions letting it shift around 2k I don't have any sounds out of the normal. If I take it to 2500-3k and it shifts there is a sound that comes from the rear end. Just wondering if anyone has come across this issue previously.