1999MB 320 4Matic trans

Stopped at a light went to start heard a loud bang car became motionless any thoughts?

Trans has 60k and never a shifting issue.

Could be a broken U-joint…you need a looksee… On your vehicle I believe the driveshafts are tucked WELL under your car…pretty much impossible to spot…however if you can see it hanging down…then you def have a broken u joint…that would disable your vehicle in one fell swoop as I believe the 4wd system is all tied together…a broken u joint would also disable the front wheels from being powered. Other than that…you could have torque convertor issues…but the bang points to catastrophic u-joint failure usually…