Sounds like limp home mode to me. Try starting out in first, and shifting when you need too...sometimes the shift valves get stuck and that will undo it (notorious with the GM 41Te if you're a tranny guru), the KA auto tranny's suck ass. If that doesn't work get somebody to test the pressures in it to see if there's a problem with low pressure (that will cause it to stay in 2nd aka Limp mode).