WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Measuring Distance From Inner Ring To Inner Groove On Shaft
Courtesy of VOLVO CARS OF NORTH AMERICA.
Wipe off the grease from the constant velocity joint housing.
Measure the distance from the inner ring to the inner groove on the shaft. Note the measurement.