CAMPAIGN:TRANSFER CASE LEAK REPLACE MACHINED ADAPTERS

MODELS: 1986 K35 LIGHT DUTY MODEL TRUCKS EQUIPPED WITH 4 SPEED MANUAL TRANSMISSIONS (RPO M20)

General Motors has determined that transmission fluid may leak from the transfer case adapter where it meets the transfer case on some 1986 K35 models, equipped with a 4 speed manual transmission. This condition may be caused by an improperly machined transfer case adapter. The bore of the adapter at the transfer case end should be machined to a depth of 25 mm.

Units that develop a leak at this area may have an adapter bore machined to only 14 mm which does not seat properly against the transfer case. To correct this condition, adapters that have been improperly machined must be replaced.

VEHICLES INVOLVED

Involved are certain 1986 K35 light duty model trucks with 4 speed manual transmission (RPO M20) built within the following VIN break points.

Model Plant Year From Through ----- ----- ---- ------- Janesville 1986 GJ522616 GJ525730 St. Louis 1986 GS523447 GS526218

The specific vechicles involved in this campaign have been identified on Vehicle Identification Number Computer Listings. These listings are furnished to all involved dealers with the campaign bulletin.

DEALER CAMPAIGN RESPONSIBILITY

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward. Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your dealership for service in the future, you should take the steps necessary to be sure the the campaign correction has been made before reselling or releasing the vehicle.

Owners of vehicles recently sold from your new vehicle inventory are to be contacted by the dealer and arrangements made to make the required correction according to instructions contained in this bulletin.

If no owner's name and address were available to GMC Truck at the time of campaign initiation, the dealer will determine the owner's name and address from the dealership sales records. Please provide this information directly on the second copy of the listing next to the applicable VIN so that our records may be updated and the appropriate notification mailed to the owner. This second copy should then be submitted to the address listed below in the previously supplied yellow campaign envelopes.

GMC Truck General Motors Corporation 101 Union Street Plymouth, Michigan 48170

OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by GMC Truck (see copy of Owner Letter included with this bulletin). A listing of owner names and addresses has been furnished to the involved dealers to enable dealers to follow up with owners involved in this campaign. This listing may contain owner names and addresses obtained from state motor vehicle registration records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to this campaign.

SERVICE PROCEDURE

Inspection:

o Disconnect the cable at the negative battery terminal.

o Raise and support vehicle on a hoist.

o Remove skid plate if equipped.

o Drain the transmission.

o Disconnect the speedometer cable at the transfer case.

o Separate the front propshaft from the transfer case. Move it away from the work area and secure it.

o Remove the shift lever linkage from the transfer case.

o Remove the rear propshaft assembly from the vehicle.

o Support transfer case with a suitable stand and remove bolts attaching it to the transmission adapter. Remove transfer case.

o Measure the depth of the adapter bore. It should be 25 mm, (Figure No. 1). If the bore depth is less than 25 mm replace the adapter. Follow replacement Procedure outlined below. If the bore depth is 25 mm, reverse the above procedure to reinstall parts. Use a new gasket between the adapter and transfer case.

ADAPTER REPLACEMENT

o Remove the adapter mount bolts from the crossmember. Lift and support the transmission so that the adapter can be removed.

o Remove adapter from vehicle. Transfer mount to new adapter. Discard old adapter.

o Using a new gasket install adapter to transmission.

o Lower transmission and bolt mount to the crossmember.

o Install transfer case to new adapter using a new gasket.

o Connect transfer case to new adapter using a new gasket.

o Connect transfer case shift linkage and speedometer cable.

o Reinstall rear propshaft assembly.

o Connect front propshaft.

o Reinstall skid plate if removed.

o Fill transmission with SAE-80W, or SAE-80W-0 GL5 lubricant, approximately 4.0 quarts.

o Lower vehicle.

o Reconnect battery cable.

TORQUE SPECIFICATIONS:

Adapter to transfer case 33 N.m (24 lb ft) Adapter to transmission 33 N.m (24 lb ft) Adapter mount to crossmember 54 N.m (40 lb ft) Skid plate to crossmember 63 N.m (46 lb ft) Transmission filler plug 23 N.m (17 lb ft) Rear propshaft front flange bolts 100 N.m (74 lb ft) Propshaft to rear axle 33 N.m (24 lb ft) Propshaft center bearing to hanger bracket 33 N.m (24 lb ft) Propshaft to transfer case 15 N.m (lllb ft)

PARTS INFORMATION

Parts are to be obtained from General Motors Service Parts Operation (GMSPO). To ensure that these parts will be obtained as soon as possible, they should be ordered from GMSPO on a C.I.O. order with no special instruction code but order on an advise code (2).

Vehicles determined to have the mis-machined adapter described in the "Service Procedure" section of this bulletin require replacement of the following parts and addition of transmission lubricant as required.

Part Quantity Number Description Per Vehicle ------ ----------- -----------

15597792 Transfer Case Adapter 1 (as required)

3901180 Gasket 1 (as required) (Adapter to transmission)

15594357 Gasket 1 (Adapter to transfer case)

NPN SAE-80W or SAE- 4 quarts 80W-90 Gear lubricant

Transmission lubricant is considered as dealer material and is entered in the net amount column on the warranty claim.

WARRANTY INFORMATION

Dealers should submit a warranty claim on each vehicle completed under this campaign.

Labor Operation *Time **Parts Trouble Number Description Allowance Allowance Code --------- ----------- --------- --------- ------- V3730 Inspect 1.6 hrs. $15.00 96 transfer case adapter only

V3731 Inspect & 2.1 hrs $15.00 96 replace transfer case adapter

With skid .3 hrs plate add

*Add 0.1 hr. to receive administration time allowance.

**This amount is to be entered as a net item to pay for the NPN SAE80 or 90, gear lubricant, required to refill the transmission.

CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this product campaign bulletin will require a "Campaign Identification Label". Each label provides a space to include the five digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or ballpoint pen.

Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner.

Apply "Campaign Identification Label" only on a clean dry surface.

ADMINISTRATIVE PROCEDURE

Procedures covering this campaign are outlined in Section V of your dealership's "GMC Truck Claims Processing Manual" #SD8519.

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Dear GMC Truck Owner:

General Motors has determined that transmission fluid may leak from the transfer case adapter where it meets the transfer case on some 1986 K35 models, equipped with a 4 speed manual transmission. This condition may be caused by an improperly machined transfer case adapter.

To correct this condition if it exists in your vehicle, the adapter will be inspected and replaced if necessary. This service will be performed for you at no charge.

Instructions for this service have been sent to your GMC Truck dealer. Please contact your dealer to arrange a service date. The labor time to inspect your vehicle is approximately 1-1/2 hours. If the transfer case adapter must be replaced it will take an additional 30 minutes. Please ask your dealer if you wish to know how much additional time will be needed to process your vehicle.

The enclosed owner reply card identifies your vehicle. Presentation of this card to your deater will assist them in making the correction to your vehicle in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid owner reply card and returning it to us.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your confinued safisfaction with our products.

GMC MUCK GENERAL MOTORS CORPORATION Enclosure 86C10

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those 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 equipment, tools, 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 a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.