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Debris in transmission extension housing may cause service alert
A recent Service Information bulletin noted that the illumination of the Service AWD lamp in select GM models (including 2018-2021 Buick Enclave, 2017-2021 Cadillac XT5, 2018-2021 Chevrolet Traverse and 2017-2021 GMC Acadia) may be the result of debris in the Transmission Extension Housing. 

Following the standard diagnostic check (DTCs C1260 through C1267, C1290 through C1293, C1295 and C1296), technicians could consider removing the Power Transfer Unit (PTU), inspecting the parts and performing a cleaning procedure.

Here are the steps to follow:

Step 1 - Remove the PTU assembly, and then remove the Shift Actuator and the Extension Housing from the assembly, discarding the latter’s seal along with the Half Shaft O-Ring Seal and Retainer.

Step 2 - Remove the Extension Housing bolts; be careful of the O-Ring. There will be some transmission fluid that will spill out of the Extension Housing — around one cup of fluid.

Step 3 - Remove the Worm Gear in the Extension Housing. Turn counterclockwise to remove.

Step 4 - Remove the Power Transfer Disconnect Rotary and Linear Cams from the Extension Housing, shaking the assembly to get the cams to slide down the intermediate shaft. Check the Linear Cam for signs of abrasion or scratches and replace if necessary.

Step 5 - Inspect the Extension Housing for internal damage, and then clean its parts thoroughly — paying close attention to the Rotary Cam Bore and Worm Gear Bore, along with the bearing at the bottom of the latter. Dry the components using compressed air to remove any remaining solvent.
 


Step 6 - Inspect the Disconnect Rotary Cam for damage to the teeth. Also, inspect the Clutch Kit: To remove, use snap-ring pliers to pull the retainer out of the groove, and a screwdriver to free it. Install a new unit into the PTU Housing spring-side out, lining up the clutch teeth with the shaft teeth in the PTU Housing. Clip one end of the retainer onto the shaft of the assembly, and use snap-ring pliers and a screwdriver to position it in the groove.

Step 7 - Install the Disconnect Rotary Cam onto the shaft, with the engagement teeth facing away from the housing. Install the Disconnect Linear Cam back onto the shaft with teeth facing the Rotary Cam and housing. Install the Worm Gear using a flat-bladed screwdriver, rotating until you hear an audible click.

Step 8 - Install a new Extension Housing seal, along with the Half Shaft O-Ring Seal and Retainer, and attach the Extension Housing onto the PTU Housing. Tighten the Hex Head Extension Housing bolts to the PTU Housing, using a crisscross pattern.

Step 9 - Inspect the PTU Shift Actuator (rotating the Worm Gear to line up with its drive) and install it, along with a new Actuator Seal, onto the Extension Housing. Tighten bolts to 10 Nm. Reinstall the PTU assembly to the vehicle, test-drive to warm to operating temperature and top off the transmission fluid. 



 
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