flare/ jump / surge between 2nd and 3rd

[PlanZero]

Whatever you want to call it, this has been happening since I got the car (97 Tsi awd) a couple months ago. If I manually shift it doesn't happen. Between 2nd and 3rd, it feels like the gears "jump", like its not shifting properly, and the rpms surge to about 3k. Sometimes happens on deceleration as well. The tranny was rebuilt or replaced 600 mi ago by the PO. I originally thought the tps might be the culprit, but I wasn't sure because when I shift manually from 2 to D this doesn't happen, plus I just haven't had the time to properly diagnose. Also, when I had the xcase off recently, I noticed an unplugged connector above the xcase, so I plugged it back in, but no difference. Any suggestions?

 

[VisegripMech]

Adding a little more fluid fixed it for me.. I was certain I had added enough, but hadn't. For two years we dealt with this, thinking it was due to my low budget rebuild. Somebody at a service station added more when I wasn't around, and now it is awesome. Just don't add too much cause it is scary when it overtops the dipstick tube and creates a ton of smoke or worse.