08 Escalade ESV clunking or rubbing sound

Sounds to me like your air ride is not working. Check to see if your ride height looks the same and if its lower than normal. If it is then you need to figure out why your air compressor is not filling the shocks with air. Could be busted shock, bad ride height sensor, bad compressor or blown fuse.

You don't always get an "service suspension system" light when you have a problem. I had a bad ride height sensor and had the same issue as you and never did have a light come on. I would start the car and let it idle 5 minutes and then reach through your rears wheels and squeeze the shock. If the rubber is not inflated enough that you cant compress the shock then your air ride is doing its job but if you can compressor the rubber on the shock then you have a problem somewhere. Your ok driving as I drove on mine for a month but its a really rough ride and slight tire rub.

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Also, if the shocks are found not be be getting air I would first check the 3-4 ride height link. It has 2 end on it and snaps onto a small round ball. Its possible one of the ends has popped of so its not tel compressor to inflate shock.