When my envoy sits overnight my rearend drops down

There has been a service bulletin for that type of concern. Here is what it states.









Suspension - Rear Suspension Is Low/Sagging/Uneven

Notes




ENGINEERING INFORMATION

Bulletin No.: 06-03-09-006B

Date: December 15, 2008
Subject:
EI06006 - Rear Suspension Uneven, Sagging, Low (Recalibrate Air Spring Sensor)

Models:
2006-2007 Buick Rainier
2006-2007 Chevrolet TrailBlazer SS
2006-2007 GMC Envoy, Envoy XL
2006-2007 Saab 9-7X


with Suspension Pkg - Rear Load Leveling (RPO G67)

Supercede:

This bulletin is being revised to update the labor operation in the warranty information. Please discard Corporate Bulletin Number 06-03-09-006A (Section 03 - Suspension).

Condition

Some customers may comment on the rear suspension being uneven or sagging.

Correction

DO NOT REPLACE THE COMPRESSOR.

Based on technician feedback, engineering has determined that the customer's concern can be corrected by recalibrating the air spring sensor. Refer to the Trim Height Uneven or Low diagnostics and Air Spring Sensor Calibration procedure found in SI.

Does it have the AutoRide feature? if so, the gas shocks used to level the rear suspension need replacing. also, you may need new rear springs, if the back is sagging below the front.

You can do a GMC Envoy Air Suspension Conversion for a fraction of the cost to stay with the air suspension.