PIP4966B

File in Section:
Service Bulletin
Bulletin No.:
Date:
PIP4966B
June, 2013
PRELIMINARY INFORMATION
Subject:
Service Malfunction Indicator Light Or Service Anti-Lock Brake System Message
Displayed In The Drivers Information Center
Models:
2007-2011 Chevrolet Silverado, Suburban, Tahoe, Avalanche
2007-2011 GMC Sierra, Yukon
2008-2011 Cadillac Escalade Hybrid
2008-2011 Chevrolet Tahoe Hybrid
2008-2011 GMC Yukon Hybrid
2009-2011 Chevrolet Silverado Hybrid
2009-2011 GMC Sierra Hybrid
Equipped with Magna transfer case NP0 NQF NQG or NQH
This PI was superseded to add inspection of the grooves. Please discard PIP4966A.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Customer may comment on a malfunction indicator light or service anti-lock brake system message displayed in the
drivers information center. Another comment may be that the speedometer is erratic or inoperative at times. During
diagnostics the vehicle may have stored a C0055 Rear Wheel Speed Sensor (both wheels) Circuit in the electronic
brake control module or a P2771 Four Wheel Drive (4WD) Low Switch Circuit in the engine control module. Concern
may be intermittent and hard to duplicate, related diagnostics may not identify the root cause.
Recommendation/Instructions
If the related diagnostics do not identify a root cause it is possible that the tone wheel for the vehicle speed sensor in
the transfer case is moving on the transfer case output shaft or the output shaft is moving.
For NQH non hybrid applications see document id 1824278 item 29 for snap ring location and item 28 for output
bearing location.
For NQH HYBRID applications see document id 1824278 item 29 for snap ring location and item 28 for output
bearing location.
For NQF applications see document id 2372510 item 36 for snap ring location and item 35 for output bearing
location.
For NQG applications see document id 2372500 item 34 for snap ring location and item 33 for output bearing
location.
The above listed snap rings are visible by removing the propeller shaft and looking up the output shaft past the rear
seal. Ensure that the snap ring is present and seated in the groove.
Excess movement of the tone wheel or output shaft, changes the air gap to the vehicle speed sensor and can cause
an erratic signal or loss of signal. Normally the tone wheel has about 1/8 inch (.125 in 3.175 mm) movement on the
output shaft but should stay centered in the opening for the speed sensor either when using a small screwdriver to
move the sensor or pushing and pulling on the output shaft.
In Some cases some customers may comment that the transfer case in the above listed vehicles grinds, growls or
disengages. Vehicle will not pull under load. Other comments may be that the transfer case will disengage upon
torque reversal i.e. shifting from reverse to drive. Customers may experience unwanted ABS activation during a
stop, loss of cruise control operation. This condition can also contribute to transmission ratio related diagnostic
trouble codes as the transmission control module is using input/turbine speed and output speed signals to calculate
gear ratio.
For NQH/NQG light duty transfer case equipped vehicles built prior to 3/16/2009 replace the output shaft bearing
and snap rings.
For NQF/NQG HD/SHD transfer case equipped vehicles built prior to 7/15/2010 replace the output shaft bearing and
snap rings.
If any of the snap rings are broken or out of their respective grooves thoroughly inspect that groove for any concerns.
Compare with the other groove, the groove depth in the shaft. Also inspect the edge of the groove to ensure that
there is no damage to the edge of the groove that would allow a repeat concern. If the groove is damaged then
replacement of the mainshaft would also be required.
Warranty Information
For vehicles repaired under warranty use:
Labor Operation
Description
Labor Time
8420470
Input Shaft Bearing Replacement
Use Published Labor
Operation Time
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.