I have a 2009 Suburban 1500 with air assisted rear suspension. I've put about 130,000 miles on it. The rear suspension isn't as stif as it used to be, making towing heavy loads difficult. What components should I replace? Do I need new springs, shocks, or both? Any advice would be appreciated

 

whats the tongue weight and trailer weight. are you using a wd hitch? hard to say without knowing what your towing?

in general........springs support weight, shocks control jounce and rebound.