Similar Problem Larry
I seem to be having the same problem with the '80 300TD I feel the shift from 1st to 2nd, but the 2nd to 3rd gear is either instantly happening right after that, engine feels sluggish at that point, then the 4th gear kicks in about 30-40 MPH. It has me stumped and I have posted it that way. Perhaps if I don't get a tech to respond to my question I will drain the fluid and torque converter and replace the filter to see if that makes the difference.
Any input from the pro's would be great to lead us along an educated guess.