Shock bushing failure in the rear can allow the shock absorber to contact the body and cause a squeaking noise over bumps in the rear. The faulty rear shock absorber bushings should be replaced.Google+
Car Problem Reports
Mercury Mariner Squeaking Noise over Bumps in Rear
Mercury Mariner Problem
Visitor, 2006 Mercury Mariner, 101,000 mi
Ford TSB # 06-20-12...enlarge to 7/8" ( 22mm. ),( Unibit drill )holes at top of shock mounts ( rear ), install mod. upper bushings & wshrs. $36 parts.,Part # 7L8Z-18198-A ( 1 kit required ) Fits '06-'07 Escape/Mariner ( Tribute? ) built before 9/5/2006. Shock upper "stud" scraping on body "thru hole". High-pitched squeak/squeal, low speeds driving. No need to repl. shocks themselves.