ron 97 vision

hello hope someone can help. I have a 97 vision with auto stick that has been a great car. just thursday the trans gave me a big problem with no indication that anything was going wrong. I was sitting in drive and deciced to back up, put car in reverse and heard a clunk-now all I have is 1st gear. If I use auto stick 1st, trans seems fine, shift to 2nd it is like neutral. does the same in drive, as soon as it shifts it is like neutral. fluid is nice and clear, is full. No reverse or any other gears, just 1st-anyone have a hint on how to diagnose the problem? is it a control module bad? mechanical problem? any help would be great.