One problem related to axle shaft has been reported for the 1998 Volvo V70. The most recently reported issues are listed below.
My wife was driving about 30 mph on a local street when she felt a pull when turning left then she heard and felt a sound like the muffler was falling off and heard a grinding noise coming from the front wheels. She immediately turned into a shopping plaza and shut off the car. What we found was that the axle nut and part of the axle had broken off and fallen out of the right front rear wheel. The wheel could have potentially fallen off and luckily she was not on a highway moving fast. The Volvo dealer believes that the cv joint for some reason (which have not yet explained) seized and caused the axle to break. The dealer recommends replacing the cv joint and bearing and the axle. The rotor was also irreparably damaged and needs to be replaced. I will keep the old parts.