Most likely you have the differential wear issue, maybe similar to the description below or maybe some other component in there:
Excessive W123 Differential Wear - Pictures
But you should also take a quick peek at your flex disks to make sure they are not almost gone.
I would do the flex disk inspection right away. While you are under there, rotate the driveshaft by hand and see how much "slop" you have back and forth. When the driveshaft turns significantly back and forth (i.e. the input to the differential) but the wheels don't turn, you obviously have a worn differential.
Flex disks are critical because they can do a lot of damage when they fail. It may be possible to hold off on the differential replacement, if required, until warmer weather.
By chance, does your car (or did it) have a harsh transmission shift? Particularly 1-2? That's what caused the differential wear you see in the linked posting.
Ken300D