GM's full sized SUVs, the Chevrolet Avalanche, Tahoe and Suburban, the GMC Denali, Yukon and Yukon XL and the Cadillac Escalade, came with several different suspension options. It can be confusing when buying replacement shocks and suspension to try to figure out if your SUV has a premium Smooth Ride or Autoride.
Every vehicle that GM produces comes with a sticker listing the alpha-numeric codes of all of the vehicle's options. These are known as RPO codes and can be very useful when trying to determine what type of suspension your GM SUV has. There are 3 different 'styles' of suspensions that these vehicles come with.
Conventional: there are numerous RPO codes for different types of conventional suspensions, the most well known being Z71 and Z66. These suspension codes are interchangeable and standard aftermarket shocks will fit any type of conventional suspension. This suspension uses the most basic components. A coil spring or torsion bar spring with a conventional gas charged shock absorber. The Bilstein Heavy Duty and 5100 Series or the KYB Monomax and Gasajust are popular performance replacements. The KYB GR2 and Monroe Reflex and Sensatrac are good quality OEM replacement shocks.
Premium Smooth Ride: indicated by the RPO code ZW7. This suspension uses a conventional suspension in the front, but the rear uses a self contained, self leveling Nivomat shock in the rear. ZW7 equipped trucks come with a softer spring in the rear since the Nivomat self leveling system does some of the work or holding the truck up. Replacing a ZW7 Nivomat unit with a standard shock requires also replacing the spring. Otherwise the truck will sag in the rear and have a much harsher ride and potentially dangerous handling.
Autoride: indicated by the RPO code Z55. This suspension system uses electronic shocks in the front that automatically adjusts to road conditions, becoming stiffer or softer as necessary. The rear will use an electronically controlled self leveling air shock that is monitored by ride height sensors and inflated remotely from an on-board air compressor.
This is an example of a RPO sticker for a GM SUV with Z55 Autoride. This sticker is always found on the inside of the glove box door. You can see the codes are in numerical order and that this vehicle came equipped with the Z55 Autoride suspension.