WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Checking Drive Shafts
Courtesy of VOLVO CARS OF NORTH AMERICA.
Pull the constant velocity joint for the drive shaft carefully to check that the drive shaft is locked into place in the differential gear.