96 Volvo GLT: CV joint changed on driver's side. Became disengaged. Found replaced joint had no slinger keeper ring. Replaced with rebuilt joint. Ran well for year. Recently it disengaged again even with slinger ring in place. Joint looked OK, so put it back against stop. Last week it disengaged again while on road. Afraid to drive now. Any ideas would be deeply appreciated. All I see that holds joint in is the slinger ring.Help Please. Thanks