It does not happen when backing up. It has always been rough going from 1st to 2nd with a bit of a jump. I have had the boden cable adjusted, which helped some. Also recently had the flex disc chaged as it was cracked.
A possible related problem is the transmission does not shift correctly at times, especially on cold start. It revs to 3000 before shifting up a gear. Once it goes through the gears one time, it is fine shifting, other than the "thud" from 2nd to 3rd.