[Stillrunning]

My 2000 Jeep Grand Cherokee which has 145,000 will not shift out of first gear (automatic Trans). I check the fluid and it was not low, does not smell burnt, but it did have alot of air bubbles. I have not had any other issues with the trans and I'm hoping this might be a simple fix and need any advise you might have. I looked in the manual and it really is not much help other then changing the fluid and replacing the filter as the first thing to try. Any ideas?