When the D indicator is flashing, it means an error has been detected in the transmission system and that is the reason for the harsh shifting.
Some scanners might not show transmission codes and some codes are not stored in the computer. Redo the scan and if it does not show, drive vehicle unit; the D flashes again and without turning off the engine, perform the scanning again.
There are no systems available that will tell you the fluids are due for replacement.
Sunday, October 10th, 2010 AT 6:39 AM