Azn: that's not what's happening... at least it wasn't in my case. I would go up a hill, it would hold 3rd... i'd crest the hill and be coming back down again, sometimes to the BOTTOM of the hill and it would never shift. that's not normal.
keep in mind... it didn't always need a hill to do this.. regular level surface streets would do it too.
2009 MINI Cooper Clubman
Nightfire Red/NFR, Tuscan Leather, CP, PP, CW, Roof Rails & Aero Kit, 16" Bridge Spokes, Xenon, Auto, English Oak Trim & Wood Wheel, Alarm, Hi-Fi
2007 Volvo S60 2.5T
2007 X3.0si PlatBronze/Beige
2006 X3 3.0i, Flamenco Red/Beige
1997 528iA, Oxford/Tan
1994 318iS, Black/Gray
1979 528iA, RubyRed, Tan
1971 2002, Sahara, Saddle