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Fila In Section: 04 - Driveling Awe
Bulletin No. 98-04-21-0068

Service Bulletin Date: September, 2002

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Subject: Transfer Case Shudder (Flush and Replace Transfer Case Fluld)

Modais: 1999-2003 Chevrolet Astro (AWD) ©
1999-2003 GHC Safari (AWD) —
1999-2001 Oldsmobile Bravada
with All-Wheel Drive (NV136) Transfer Case (APO NP4)

This bulletin is belng revised to add model years. Please discarc) Corporate
Bulletin Number $9-04-21-005A (Section 04 — Driveline Axle).

Condition Perform ihe following diagnesie prior to flushing and
Some custammers may comment about a vibration replacing the transfer case fluld In order to property
(shuader) dusing tight tuming maneuvers on dry identéy the shudder.

pavement at vahicle epeeds lees than 6 km/h {5 mph), Diagnosis

Cause 1. Verify the shudder in the vahicle. The vehicle needs
This condition may be caweed by a slip-stick of the to be at operating temperature (driven at least
clutch plates In the transfer case clutch pack. On 1899 5 miles} for proper diagnos, After the vehicle is
and meawer models, the preload that is dealgned into at operating temperature, drive In a tight circle
thre clutch pack may contrifute to the condition. In Just short of steering wheel lock, at a speed less
addition, contamination of tha fluid may interfere with than & kevh (5 mph) in ander to identity the

the friction medifiars, shuckter.

Correction 2. Wentfy whet rear axe type the vehicle has.
Flush and replace the tranetar case fluld on affactad * ifthe vehicle has @ standard reer axe, than
vehicks using the following procedure and the part proceed to step 3.

number iisted below.

Gopyiget 2007 Geneva! iWoters Gomensiion. Al Figtes Alaaaneec,

Page 2 September, 2002 Bulletin No.: 99-04-21-005B

= If the vehicle has a locking rear axle, remove 3. After refilling the transfer case, drive ihe vehide a
ee ron propeller shaft. aoe ta the Progaller minimum of & km (5 mij.
aft subsection In the Service Manual. Drive ,
. ne 4, With the transfer case at operating temparature, @
the ete eau In step . stall the front drain the transfer case flukd again.
propeller shaft and procuad to step 3. 5. Refill the transfer case with new fluid.
Refer to the Propeller Shaft subsection i = important: The vehicle may require approximately
the Service Manual. 160 km (100 miles) of driving bafare the condition is
+ It the shudder does not po away, the completely corrected,
Rev the eee ie ee 6. If this procadura doas not correct the shudder
determine if the rear ade was servicad condition, please call ihe Technical Assistance
at the first scheduled oll change. If Genter for further Instructions.

records indicate that tha axle service was
done, then revaluate the condition using Parts Information
diagnostic information in ihe appropriate

Servica Manual. If the rear ade wes Part Number Description Qty
not serviced, service the rear ade. 12579503

INFORM THE CUSTOMER THAT THE (Canadian | Ae | containers
AXLE SEAVICE IS AN OWNER'S PAN 10853626)

MAINTENANCE ITEM NOT COVERED
WNGER THE VEHIGCLE'S WARRANTY, Parts are currently available from GMSPO.

« Install tha front propeller shaft. Refer to
the Propeller Shaft subsection In the Warranty information

Sarvica Manual. For vehicles repaired under warranty, Use:
3. Flush tha transfer case with the blua colored fluid
(ALTTO-TRAK II} using the procedure ard part Labor
number listed belaw. Perform the flush procedura Operation Description Labor Tana
even if the transfer case contalns the biue colored “Add Teat Drive Vehicle te Identity 04 br
AUTO-TRAK II fluid in order to remove any possible Shudder

contaminants. The AUTG-TAAK i fluld contains Add To Diagnose Shudder with 06 br
BA improved friction modifier that should correct the Locking Aear Ade
silp-stick condition. Refer to the Transtéer Case Add To Flush/Aeplace Transtar OF hr
subaection In the Service Manual for information an __—_ Cras Auld !
draining and filling the transfer case. This is 4 unique labor operation numiber for use only with
thie bulledn. This number wil not be publiehad In ihe
Flueh Procedure Labor Time Gulde.

Important: Refer to Corporate Bulletin Number
96-04-21-001, dated April 1999, for important
Information on ramoving the tranefer case drain and

fill plugs.
1. Grain the transfer case fluid.

2. Rafi the transter casa with 2 L (2 qts} of naw fluld,
PAN 12378506 (Canadian P/N 10953626).

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