Noting to do with the air.... its in the rear, ac can be on or off... its the same regardless.

 

I noticed that you were instructed to tap the exhaust system at several locations with a hammer and that you just shook it by hand.
Different frequencies produce different sounds.
Try tapping with hammer and listem for looseness IN the exhaust system

 

I don't know how the driver can pinpoint an exterior noise to the rear. My vote is flex pipe or that crappy weld near it. Bad hubs sometimes present as "buzzing", as do tires and plastic bags hanging from the axle and RC cola caps stuck in the alternator. (all previously posted phantoms)

 

well I know it has a bad hub and tie rod.... got the parts just waiting to get those changed out soon
. LCA seem to be bad as well, crappy handing recently as well, so going to order those soon.

 

yup smashing with a mallet no rattles

 

Bad hub, buzzing, bad LCA’s rear bushings clunking, swaybar end links rattling and clunky. Wait till you change those parts. See if the noise disappears

 

I agree, but hard for me to say the front parts are causing the noise to appear in the rear only, just a really odd buzz only during accelerations. Say like taking off on a slight incline, the buzzing is super loud ( sounds almost metallic ) let off the gas or give it more gas and it goes away or once it shifts to the next gear it stops, but will come back when its near a shift point as well at any speeds. The odd part is, it sometimes doesn't do it but it doesn't matter if the ac is on or off, hot or cool out, highways, side streets, speed.... it comes and goes at various times and some days it doesn't do it at all. It doesn't have me worried of a break down or anything like that but I just hate this damn annoying buzzing sound, its loud when it does it and its originating in the rear only and local to the right side ( passenger side )
Im thinking to go for a drive and let my son sit in the back and crawl around to pinpoint the area to narrow it down but that could be a hit and miss as well since I cant find anything loose visually and manually inside or out but maybe Im missing something if its behind a panel like a connector up against something?

 

Right rear, have a look down behind the seat where it folds forward, possibly something rolled down into that area

 

Could it be something to do with the vent valve?

 

I already checked all that since I had a tube of caulk roll under from the back, a bit of a pain to fish it out but got it... I looked for other stuff that maybe a previous owner lost, it was clean and nothing to be found. so under the rear seats is good.