No, the RF coax does not connect the TV audio to the surround amplifier/DVD unit. Attached is the connection diagram for these GS coaches. You can see that the audio L & R signals from the original TV came back to the amp via the stereo RCA connections.
Many of the newest TVs do not have these outputs -- they have either HDMI with "return channel" or a separate fiber optic audio connection. Can you post an image of the connection panel of the TV you have used for a replacement? What make/model is it?
2007 Tour Master T40C
Acura MDX toad
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