Does it sound like it's slipping? A girl I know had the same thing happen to her, between 2nd and 3rd. Turned out, it was her TCU(computer for tranny). If she would shift manually, the transmission worked fine. Try that, see if there is a difference.
If that doesn't work, PM me. I just pulled out my original AT, and I'd sell it to you at a reasonable price. I just put in my H22A AT w/LSD today.
