If the fluid looks and smell bad, try doing a complete flush or a drain and fill. If the reverse does not work, then maybe you should have it diagnosed to see what's wrong. If you want to rebuild the tranny, then I'd recommend just replacing it w/ a used low milege tranny. It'll save you possibly thousands depending on where you go. Is the fluid full on the tranny? Sometimes this may cause a car not being able to move at all.