Hey all.. I currently have a express 1500 van with stock radio and 2 front speakers only. In the back, above the back door there is a connection for left and right speakers. Also, on the drivers side rear, right near the brake/reverse lights there is an additional speaker connection but there is not another one on the passenger side. Can someone tell me what this odd connection is for?

 

I know the speaker connection for above the back doors is on the right. In other vehicles that I have explored the connection you speak of on the driver side/rear has gone to speakers mounted "inside" the rear doors.