I have a 2013 1500 Suburban LT 2wd. It has an RPO code ZW7 premium smooth ride, from which many indications is supposed to have the nivomat shocks on the rear and also a weaker rear spring. It does not have the nivomat shocks. When a dealer looks up part numbers from the VIN, it does not require the special nivomat shocks (just a standard shock at about $70 vs. the $300 nivomat. Trying to find out if this is standard "ZW7 without nivomat shocks". I am having sway issues towing a 6000lb travel trailer. I did not have these same issues with a 2004 Tahoe or with a 2005 1500 Suburban with the same trailer.