I replaced my rear air suspension on my 04 a couple years ago. I just bought normal rear shocks and springs for a non-air suspension model. I secured the air lines to the frame and disconnected the relay to the air compressor.
www.jegs.com
this is the springs I used. Any gas shock would work in place of the air shocks.
Moog 81085: Rear Coil Springs 2007-2010 Nissan Armada - JEGS High Performance
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this is the springs I used. Any gas shock would work in place of the air shocks.