GM Bulletin No.: 13346
Date: November 2013

Service Bulletin

SERVICE UPDATE
SUBJECT:

Service Update for Inventory and Customer Vehicles
4-Wheel Drive Transfer Case Adapter Housing
Expires with Base Warranty

MODELS:

2013 Chevrolet Silverado HD
2013 GMC Sierra HD
Equipped with 4WD and 6-Speed Automatic Transmission (MW7)

This service update includes vehicles in dealer inventory and customer vehicles that
return to the dealership for any reason. This bulletin will expire at the end of the involved
vehicle's New Vehicle Limited Warranty period.
PURPOSE
This bulletin provides a service procedure to inspect the transfer case adapter housing for two
specific build codes on certain 2013 Chevrolet Silverado and GMC Sierra HD vehicles,
equipped with 4WD and 6-speed automatic transmission (MW7). If the housing has one of the
two codes, dealers are to test drive the vehicle and, if necessary, install a new transfer case
adapter housing.
The front and rear machined surfaces of the transfer case adapter housing on these vehicles
may not be parallel to each other. This could cause harsh downshifts, a "bump" feeling when
coasting, or a grinding noise on deceleration. These conditions may be more noticeable in the
tow/haul mode and when using engine braking without using the service brakes.
This service procedure should be completed as soon as possible on involved vehicles
currently in dealer inventory and customer vehicles that return to the dealer for any type
of service during the New Vehicle Limited Warranty coverage period.
VEHICLES INVOLVED
All involved vehicles are identified by VIN in the Global Warranty Management System –
Investigate Vehicle History Application. Dealership technicians should always check this site to
confirm vehicle involvement prior to beginning any required inspections and/or repairs. It is
important to routinely use this tool to verify eligibility because not all similar vehicles may be
involved regardless of description or option content.
Copyright 2013 General Motors. All Rights Reserved.

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November 2013

Bulletin No.: 13346

Additionally, a list of involved vehicles currently in dealer inventory is available on the “Service
Update Bulletin Information” link under the “Service” tab in GM GlobalConnect (US) or attached
to the GlobalConnect message (Canada) used to release this bulletin. Customer vehicles that
return for service, for any reason, and are still covered under the vehicle's base warranty should
also be checked for vehicle eligibility.
PART INFORMATION
Parts required to complete this service update are to be obtained from General Motors
Customer Care and Aftersales (GMCC&A). Please refer to your “involved vehicles listing”
before ordering parts. Normal orders should be placed on a DRO = Daily Replenishment Order.
In an emergency situation, parts should be ordered on a CSO = Customer Special Order.
Part Number
24258440
29536941
29547443
88861037-US
19264717-CA
24263164

Description
ADAPTER, TRFER CASE
GASKET, A/TRNS CASE EXTN
NUT, OUTPUT SHF RET
FLUID, A/TRANS DEXRON VI

Quantity/Vehicle
1
1
1

GASKET, TRFER CASE ADAP

1

88996648

RETAINER, TRANS FLUID CLR PIPE CONN

2

29536834

SEAL, TRANS FLUID FIL TUBE

1

15126137

GASKET, CTLTC CONV

1

22913281

CLAMP, PROP SHF SLIP YOKE BOOT

2

15898003

RING, PROP SHF UJT SPIDER BRG RET

4

11611401

BOLT, TRANS MT

2

12

SERVICE PROCEDURE
1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in SI.

3638070

2. Locate the traceability number on the transmission low reverse clutch housing (1). The
traceability number was written with a black paint marker.

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November 2013

Bulletin No.: 13346

3638064

Numbers shown in the photograph above do NOT fall under the suspect parts. (1) Location of
Traceability Numbers. (2) Machine Number (3) Fixture Number (4) Shift Sequence Number (5) Machine
Julian Date.

3. Determine the traceability number written on the low reverse clutch housing. The number
includes a machine number, fixture number, shift sequence number and machine Julian
date. Refer to the photograph to review the breakdown of the traceability number.


If the traceability number includes a machine and fixture number of black 31 or 32 and
machine Julian date of 254, proceed to step 4.



If the traceability number includes machine and fixture numbers other than black 31 or 32
or a Julian date other than 254, no further action is required. Lower the vehicle. Refer to
Lifting and Jacking the Vehicle in SI.

4. Drive trucks in tow/haul mode with exhaust brake enabled for 10 minutes.
4.1 Reach a speed of 89 km/h (55 mph).
4.2 Decelerate (coasting at zero throttle to utilize engine braking, no service braking) from
89 km/h (55 mph) for 10-15 seconds. Repeat deceleration from 72 km/h (45 mph).
Perform on a slight downgrade where possible.
4.3 Observe transmission operation for harsh downshifts, a periodic slip/bump that may be
described as if a heavy weight were dropped in the bed of the truck, or the vehicle was
rear ended. The transmission may also produce a grinding or rattle noise.


If the test drive produces these symptoms, replace the 4WD extension housing.
Proceed to step 5.



If the test drive does NOT produce these symptoms, no further action is required.
Lower the vehicle. Refer to Lifting and Jacking the Vehicle in SI.

Note: The transmission MUST be removed from the vehicle and placed on a stand with the rear
of the transmission pointing up to replace the low reverse clutch housing.
5. Remove low reverse clutch housing. Refer to Low and Reverse Clutch Piston and Output
Carrier Assembly Removal in SI.
6. Install new low reverse clutch housing. Refer to Low and Reverse Clutch Piston Housing
Installation in SI.

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Bulletin No.: 13346

WARRANTY TRANSACTION INFORMATION
Submit a transaction using the table below. All transactions should be submitted as a ZFAT
transaction type, unless noted otherwise.
Labour
Code
9100214
9100215
9100216

Description
Inspect Traceability Number – No Further Action Req'd
Inspect Traceability Number & Test Drive Audit – No Further Action
Req'd
Replace Low Reverse Clutch Housing (inc. inspect & test drive audit)

Labour
Time
0.3
0.5
7.2

DEALER PROGRAM RESPONSIBILITY
Whenever a vehicle subject to this service update enters your vehicle inventory, or is in your
facility for service in the future, and the vehicle is still covered under the New Vehicle Limited
Warranty, you must take the steps necessary to be sure the service update correction has been
made before selling or releasing the vehicle.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that
may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the tools,
equipment, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to
your vehicle, or that your vehicle will have that condition. See your dealer for information on whether your vehicle may benefit from the information.

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