Low Frequency High Pressure Boom Or First Order Driveline Vibration At Speeds Above Approximately 40MPH - keywords prop shaft
| Subject: | Low Frequency, High Pressure Boom or First-Order Driveline Vibration at Speeds Above Approximately 40 MPH |
| Models: | 2008-2009 Cadillac CTS |
This PI was superseded to update model years and diagnostic procedure. Please discard PIP4444.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may comment on a low frequency, high pressure boom, like driving with a rear window part way down, or a vibration when driving at speeds above approximately 40 mph. This condition is present over a wider speed range than the concern described in the most current version of PIP4435. This condition is not affected by whether or not the TCC is turned on and may even be present in vehicles equipped with manual a transmission. This condition may be present when coasting down through the speed range with the transmission in neutral. Following the procedures in SI Document ID 1578894, "Diagnostic Starting Point - Vibration Diagnosis and Correction", may indicate a first order driveline disturbance.
Recommendation/Instructions:
Verify the concern by duplicating the condition. If diagnosis using the J 38792-A, Electronic Vibration Analyzer (EVA) 2 confirms a first order disturbance, check for a propshaft issue by indexing the propshaft to the other two of the three positions. If the condition varies in intensity with the propshaft indexed to the other positions, or if the condition changes by substituting a propshaft from a known good vehicle, perform the procedure in SI Document ID 1579481, "Driveline System Balance Adjustment (Using EVA)". If the prop shaft cannot be properly balanced using the EVA and swapping and or indexing the prop shaft did change the concern replace the prop shaft. In all cases, the rear drive axle SHOULD NOT be presumed to be the cause of the vibration unless the propshaft is completely eliminated as a potential cause.
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.
