Using Tmpeg to make a mpeg2 out of a DVD

1_1.VOB
1_2.VOB
1_3.VOB
are the main movie files. 1_1.VOB is used for the video source
and the audio source. it makes a mpeg2 about 45 minutes long.
but when I try to get the rest of the video and audio using the other
VOB file as in 1_2 and 1_3 the audio is not there for these files.
only the video is. I have even tryed using the 1_1.VOB as the audio
source but I get the first 45 minutes of audio if I do that.
not sure where the rest of the audio is for the rest of the movie.
Im baffeled