I remember in my last vehicle that the whining sound may be a grounding loop from something in the truck not having a good enough ground path, so it grounds out over your rca cables. I would do to things: Ensure the head unit is grounded directly to the chassis and scour your wires for grounding issues... Welcome to the forum!

 

you mentioned the battery needs replacing, I would say that is you alternator creating the whine, it is charging hard...once the battery is replaced you should be good

Not sure if you need the airbags, I did the coil conversion and never a problem....I am sure some purists will chime in but I personally don't see the use of rear airbags. I pull a 24 foot trailer around from time to time, no issues

 

Got a new battery but it didnt fix the whine..... It stops once i get up past 60 on the freeway. While at the dealer he took a look at it and said it is the aftermarket amp. I think I will have it removed. I am thinking they put it in there for the DVD player.... maybe it wasnt loud enough when they watched movies.

 

Here are a few pics of my son, his Hummer....... my adopted son and his new Civic. It was a good Christmas for my boys... LOL.

 

I really like the red color! I had an inferno red Grand Cherokee a while back and wish my H2 was the sam color. Thanks for sharing!