My car is shifting hard from 1st to 2nd, and down from 2nd to 1st. It doesn't do it all the time, but sometimes, and it's way too hard. Someone just mentioned today that it might be the transmission module, that it might need replaced.

Can anyone chime in on this?

jeff 1991 300d 188k

Does it hold vacuum?

You could tee in to the line and see if you're getting steady vacuum to the modulator while driving.