CAMPAIGN:TRANSFER CASE LEAK REPLACE MACHINED ADAPTERS

MODELS: 1986 K30/35 Trucks with M20 4-Speed Manual Transmission

DEFECT INVOLVED:

General Motors of Canada has determined that transmission fluid may leak from the transfer case adapter where it meets the transfer case on some 1986 GMC K35 and Chev. K30 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 and K30 Light Duty Model Trucks with 4-speed manual transmission (RPO M20) built within the following VIN breakpoints:

Model Model Plant Year From Through ----- ----- ---- ---- ------- GMC K35 Janesville 1986 GJ522616 GJ525730 GMC K35 St. Louis 1986 GS523447 GS526218

Chev. K30 Janesville 1986 GJ158955 GJ167154 Chev. K30 St. Louis 1986 GS170442 GS176924

All affected vehicles have been identified by the VIN listing provided to involved Dealers with this bulletin. Any Dealer not receiving a listing was not shipped any of the affected vehicles.

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 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 modification according to instructions contained in this bulletin.

CAMPAIGN PROCEDURE:

Refer to Section 4 of the Service Policies and Procedures Manual for the detailed procedure on handling Product Campaigns. Dealers are requested to complete the campaign on all transfers as soon as possible.

OWNER NOTIFICATION:

All owners of record at the time of campaign release are shown on the attached computer listing and have been notified by first class mail from General Motors. The listings provided are for campaign activity only and should not be used for any other purpose.

PARTS INFORMATION:

Parts required for this modification should be ordered through regular parts channels.

Vehicles determined to have the mis-machined adapter described in the "Service Procedures" 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

PARTS AND LABOUR CLAIM INFORMATION:

Credit for the campaign work performed will be paid upon receipt of a properly completed campaign claim card or RAPID terminal transmission in accordance with the following:

Repair Code Operation Time Allowance ----------- --------- -------------- 2A Inspect transfer case 1.7 adapter only.

3A Inspect and replace 2.2 transfer case adapter.

If vehicle is equipped with a skid plate, please process an add credit for an additional 0.3 hrs.

Time allowance includes 0.1 hour for Dealer administrative detail associated with this campaign. Parts credit will be based on Dealer net plus 30% to cover parts handling.

SERVICE PROCEDURE:

Inspection:

---------- 1. Disconnect the cable at the negative battery terminal.

2. Raise and support vehicle on a hoist.

3. Remove skid plate if equipped.

4. Drain the transmission.

5. Disconnect the speedometer cable at the transfer case.

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

7. Remove the shift lever linkage from the transfer case.

8. Remove the rear propshaft assembly from the vehicle.

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

10. 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

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

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

3. Using a new gasket install adapter to transmission.

4. Lower transmission and bolt mount to the crossmember.

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

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

7. Connect transfer case shift linkage and speedometer cable.

8. Reinstall rear propshaft assembly.

9. Connect front propshaft.

10. Reinstall skid plate if removed.

11. Fill transmission with SAE-80W, or SAE-80W-90 GL-5 lubricant, approximately 4.0 quarts.

12. Lower vehicle.

13. 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 46 N.m (40 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 centre bearing to Hanger brkt. 33 N.m (24 lb. ft.) Propshaft to transfer case 15 N.m (11 lb. ft.)

INSTALLATION OF CAMPAIGN IDENTIFICATION LABEL

Clean surface of radiator upper mounting panel and apply a Campaign Identification Label. Make sure the correct campaign number is inserted on the label. This will indicate that the campaign has been completed.

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.