Subject: | Exhaust Vibration, Resonance, or Moan |
Models: | 2001-2006 Cadillac Escalade |
2002-2006 Chevrolet Avalanche |
1999-2006 Chevrolet Silverado |
2000-2006 Chevrolet Suburban, Tahoe |
1999-2006 GMC Sierra |
2000-2006 GMC Yukon |
2003-2006 HUMMER H2 |
This PI has been revised to include the 2006 Model Year. Please discard any copies of PIP3121D.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Some 1999-2006 C/K sport utility vehicles and trucks with GEN III V8 Engines and a single pipe exhaust system may exhibit an exhaust vibration that is engine load sensitive. Typically, this will happen just off of idle to 2000 RPM on light acceleration.
Important: The following does not apply to 2003-2006 Full Size C-K Utility Vehicles with an IDLE ONLY vibration. Reference PIT3203E for IDLE ONLY vibrations on 2003-2006 Full Size C-K Utility Vehicles.
Important: The following does not apply to dual pipe exhaust systems like the ones used on some 3/4 Ton and 1 Ton trucks or like the ones used on the SS Chevrolet Silverado or the GMC Denali Pick Up Truck.
Here is an example of a 4th order vibration at 900 RPM:
58 Hz multiplied by 60 = 3480
3480 divided by 900 RPM = 3.87
3.87 Rounded Up = 4
4 = 4th Order Engine Vibration
If this is a 4th order vibration, fabricate 2 dampers using the following procedure:
Note: The locations above are just starting points. If the vibration is not improved, move the dampeners around while using an EVA tool to fine tune the exhaust system by noting the G readings on the exhaust system.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.