for those interested, turns out that Richard Sexton was right on the money. However, not the flexdisk but the center bearing. I fixed it by simply driving on the freeway for a few km. turns out sliding into the snowbank had gotten some snow/ice onto or into the bearing. Then the weather got cold (-15C) and there was probably a little corrosion on the bearing plus the cold weather making the whining noise around 50 to 60 kph. As soon as I drove it on the freeway (worried about doing this at first) I could hear the noise diminish
cheers, guenter