what is wrong with sprinter 310 V reg?

with no warning a rattle occured around the gearbox. when clutch was pressed the noise went away. when driving up through the gears there was an awfull vibration. I asked a mechanic and was told it may possible be the thrust bearing. fearing the worst i stopped driving it. when i drove it to the garage today for another mechanic to listen to it, the noise has gone and so has the vibration. could it be the fly wheel. Has this model got a dual mass fly wheel.