Does anyone know where the Sirius receiver box is in my 2006 3500 megacab dually diesel? I need to find it to extend the antenna cable so that I can get reception with my camper on. It’s not above the glove box or behind the right kick panel.

Well, in the service manual, it shows up under the rear seat (or behind the seat) in the Quadcab. I actually found mine right behind the Glovebox. The actual antenna wire (i think in all cases) goes down the right rear pillar. You may want to look for the antenna wire and see where it takes you.
Good luck

I think its tied right into the deck but I could be wrong.

I found mine in my old 06 by taking out the back seat and pulling everything apart back there because of the stupid service manual. I followed the wire into the passenger kick panel and eventually found it behind the glove box. I will have to check the new truck and see if it back there as well.

Thanks for the help. I also pulled out the back seat and followed the wire and it turns out that it was over the glove box. I saw it up there when I first started looking, but didn't recognize it becuse of the metal plate on the bottom and the antenna connector, which looks totally different from the connector on the extension antenna I bought. I couldn't get the damn thing off either, without breaking it. However, the extension antenna fit and now it's mounted on the hood and hopefully I can get reception with the camper on.

Glad to hear it. I accidentally ripped my antenna wire in half in the door sill in my old truck, I can speak from experience when I say that you can splice it without any adverse effects.