1st, the history. I use Tiptronic almost exclusively (better mileage with lower rpm shifts).
70K bought used, fluid/filter change with Mobil. No change, shifted like stock.
100K , fluid/filter change with Redline D4. Smoother shifting, much smoother downshifts into 1st. 2 long road trips this summer (9000 miles) including lots of mountian driving, no problems.
115K (2 weeks ago), noticed the rpm float/climb while upshifting under part throttle. Slightly worse when warm, it would rise up to 400rpm. TC stayed locked while in gear.
Last Sunday, out for a Sunday Morning Drive (think canyon run). At 90-100mph, TC starts to unlock in 5th and revs climb 400 rpm. Shut down for lunch, normal speeds on the drive home and it seemed fine.
Yesterday, take it Sipes, 40 miles up, 20+ hard miles while being scanned. All seems normal, no trans codes just the usual Cat code and a new secondary air flow problem. TC shows locking when it should. Trans temp rises to 90c and stays (as it should).
Drive 40miles home in near stop and go highway rush hour traffic. Get within 10 miles of home and traffic opens up. Get up to 60 and notice revs are climbing too high. 2500 at 60 and it jumps to 2800 if I push the gas. The rest of the drive home, the TC will not lock in any gear.
Drive to work this AM and car is fine
It seems similar to this W8 thread about a failed TC.
I guess we are taking the Golf on this weekend's trip to Austin.