The way this thing acts, though, depends on operating conditions. For instance, if it is wet outside, upon acceleration the driveshaft will not rumble as roughly.

In the cold and damp, the vibration almost disappears completely altogether.

* The driveshaft is three-piece, and it has traction control (ASD).

The car has 244K miles. It has had this vibration for the past 20K miles, and it has not gotten any better, or worse.