You must have the Big Tow package. It includes heavy duty air shocks on the rear and self leveling. The air was releasing to lower the rear to the proper level when you removed the load. You will also hear the air compressor running to raise the rear when you place a heavy load in the Armada. The compressor is located under the Armada, on the driver side, behind the rear axle. This is another nice feature on our Armadas.