A/T - Chuggle/Shudder On Hard Acceleration
TECHNICALBulletin No.: 09-07-30-001E
Date: June 26, 2012
Subject: Transmission Shudder or Bucking Feel (Follow Procedure Outlined Below)
Models:
2009 Cadillac Escalade
2008-2009 Chevrolet Tahoe
2008-2009 GMC Yukon
Equipped with 2 Mode Hybrid Automatic Transmission (RPO M99)
Built Prior to Serial Date 8010017028
Supercede:
This bulletin is being revised to update the Condition. Please discard Corporate Bulletin Number 09-07-30-001D (Section 07 - Transmission/Transaxle).
Refer to the illustration above to locate the sequential serial number (6).
Condition
Some customers may comment that the vehicle has a shudder, bucking or surge feel (similar to a severe engine misfire) when driving with the internal combustion engine running. The concern may be more noticeable in cold ambient temperatures and with transmission cold, but may also be present after the vehicle and transmission are up to operating temperature. The concern can also be noticeable at highway speeds.
Cause
This condition may be caused by a restricted line pressure decrease orifice.
Correction
To verify the concern is caused by the orifice, monitor the Hybrid Low 1-2 clutch slip speed (clutch 1 on the scan tool). Normal clutch slip speed should be 0 rpm. If the slip speed varies either positive or negative slip rpm, or causes other clutch slip speeds to read erratic, the orifice is most likely restricted (see scan tool screen shot below showing variation of the clutch 1 slip speed (circled area). Normal reading would have a flat line (0 rpm).
1. Remove the transmission.
2. Separate the torque dampener housing from the transmission.
3. Remove and discard the orifice cup plug in the pump cover. The location is shown above (callout #4).
4. Replace the pressure regulator valve inner spring. The spring is shown as part number 234 in the picture above.
5. Install the torque dampener housing to the transmission.
6. Install the transmission.
A new spring can be obtained through the Warranty Parts Center; you will need to E-mail or fax a completed Warranty Parts Center (WPC) request (shown below). The WPC part number is #573 and the WPC will ship you one spring.
IMPORTANT NOTE WHEN PRINTING THIS FORM: If the form prints out on two pages, make certain you fax BOTH pages so the WPC receives all the needed information. Missing information will delay or prevent the part from being shipped.
Warranty Information
For vehicles repaired under warranty, use.
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