I just had my clunk repaired at Volvo Dealership in Mississippi. It would hestitate from 1st to 2nd, then drive perfectly. As time went on, approximately 2 months, it got worse and then the alert message appeared "service Tranmission uregent". $5049.00 later I had to have a new transmission, alternator and module that goes with the transmission.
I have NEVER had a problem with my 01 XC70 CC AWD til now.... it has 130,000 miles and the new transmission is under warranty for 12 months....
Hope your problem is minor and a less costly one than mine..........