SOFT CRANKSHAFT SPROCKETS (NO HEAT TREATMENT)

Subject: SOFT CRANKSHAFT SPROCKETS (NO HEAT TREATMENT)

Models: 1993 Chev & GMC Trucks With 7.4L Engines (VIN Code N)

TO: ALL GENERAL MOTORS DEALERS:

General Motors of Canada Limited has determined that certain 1993 C/K trucks with the 7.4L gas engines may have been built with soft crankshaft sprockets not properly hardened. Non-hardened crankshaft sprockets can cause excessive wear and may result in an engine failure.

To prevent this failure from occurring, dealers are to replace the crankshaft sprocket. In the event that the truck is towed in and it is determined that the crankshaft sprocket has failed, the engine should be replaced. To replace the engine, call your Technical Assistance Department for a new engine replacement and special instructions.

VEHICLES INVOLVED:

Involved are forty-seven (47) 1993 Chev & GMC C/K trucks equipped with option (L19) 7.4L TBI gas engine.

NOTE: PLEASE CHECK DCS SCREEN 45 BEFORE PERFORMING CAMPAIGN TO ENSURE THAT THE VEHICLE IS AFFECTED. ONLY AFFECTED VIN'S WILL BE PAID.

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:

All unsold new vehicles in dealer's possession and subject to this campaign must be held and inspected/repaired per the Service Procedure of this Campaign Bulletin before owners take possession of these vehicles.

Dealers are to perform this campaign on all involved vehicles at no charge to owners, regardless of kilometres traveled, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your new vehicle inventory with no owner information indicated on the dealer listing, are to be contacted by the dealer, and arrangements made to make the required correction according to instructions contained in this bulletin. This could be done by mailing to such owners a copy of the owner letter accompanying this bulletin. Campaign follow-up cards should not be used for this purpose, since the owner may not as yet have received the notification letter.

In summary, whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

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 (see copy of owner letter included with this bulletin). The listings provided are for campaign activity only and should not be used for any other purpose.

PARTS INFORMATION:

NOTICE: DUE TO THE LIMITED NUMBER OF INVOLVED VEHICLES, PARTS SHOULD BE ORDERED BASED ON INVOLVED VEHICLE LISTINGS.

Parts required to complete this campaign should be ordered through regular channels, as follows:

Part Number Description Quantity/Vehicle ----------- ----------- ---------------- 3902426 Crankshaft Sprocket 1

10114161 Front Cover Gasket 1

14103224 Timing Chain 1 (If Required)

330814 Camshaft Sprocket 1 (If Required)

25013977 Oil Filter (PF1218) 1

993182 Oil, 10W-30 5 Litres

23011420 Magnetic Drain Plug 1 (If Required)

3860039 Water Pump Gasket 2

PARTS AND LABOUR CLAIM INFORMATION:

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

Failed Repair Code Description Part No. Time Allowance ----------- ----------- -------- -------------- 2A Replace Crankshaft Sprocket, 3902426 2.7 Oil and Filter 10114161 25013977 993182 3860039

3A Replace Crankshaft Sprocket, 3902426 2.7 (Camshaft Sprocket, Timing Chain, 10114161 Oil Pan Plug if required - use 330814 Repair Code 7A), Oil and Filter 14103224 23011420 25013977 993182 3860039 4A Replace Engine 6.2

NOTE: IN THE EVENT THAT THE TRUCK HAS BEEN TOWED IN AND IF IS DETERMINED THAT THE CRANKSHAFT SPROCKET HAS FAILED, CONTACT YOUR TECHNICAL ASSISTANCE DEPARTMENT AT 1-800-263-7740 WHO WILL COORDINATE OBTAINING A NEW ENGINE AND PROVIDE NECESSARY SPECIAL INSTRUCTIONS.

Time allowance includes 0. 1 hour for dealer administrative detail associated with this campaign. Parts credit will be based on dealer net plus 30%. An allowance of $11.73 is included in Repair Code 2A and 3A for Purolator Air Freight to return the sprockets, also an amount of $565.00 is included in Repair Code 4A for parts handling.

SERVICE PROCEDURE:

1. Remove torsional damper and front cover per the 1993 Service Manual, Section 6A5, using tool J-39046.

NOTICE: EXTREME CARE SHOULD BE USED WHEN REMOVING FRONT COVER FROM ENGINE BLOCK TO PREVENT DAMAGE TO OIL PAN GASKET. OIL PAN GASKET IS ATTACHED TO FRONT COVER AT RTV JOINTS.

2. Remove crankshaft sprocket using tool J-28509-A (Ref: Section 6A5).

3. Inspect crankshaft sprocket for excessive wear. Place new crankshaft sprocket and crankshaft sprocket removed from truck on a flat surface on edge (see illustration #1). If old gear is 1/8 (0.125) inches smaller, go to step #4. If old gear is the same or less than 1/8 (0. 125), go to step #5.

4. Install new crankshaft sprocket, camshaft sprocket and timing chain using tool J-22102, and magnetic drain plug.

5. Install new crankshaft sprocket only, using tool J-22102.

6. Install front cover and torsional damper. (Ref: Section 6A5)

7. Change oil and filter.

8. Install campaign label.

9. Return only the crankshaft sprocket using Purolator Prepaid Air Freight, with legible copy of work order with VIN, mileage and date replaced to:

General Motors of Canada Limited TAC - Chassis Truck Group 163-010 1908 Colonel Sam Drive Oshawa, ON L1H 8P7

IMPORTANT: If engine exchange is required and approved through the Technical Assistance Department, refer to Service Manual, section 6A, for procedures. The campaign label is to be installed after engine replacement.

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.

Dear General Motors Customer

As a valued customer, your complete satisfaction with your Chevrolet/GMC Truck is our goal. In keeping with this goal, we want to let you know that we have discovered a problem that could affect your vehicle and we want to take care of it at no-charge to you.

On a number of 1993 C/K Pickup Trucks, equipped with 7.4L engines, such as yours, the engine crankshaft sprocket may not have been properly hardened. This condition could result in excessive sprocket wear and may cause an engine failure.

To be absolutely sure that your vehicle is to specifications, whether it has the problem or not, we will install a new crankshaft sprocket and change the engine oil and oil filter.

This service will be provided for you at no charge.

Please contact your GM dealer as soon as possible to arrange a service date.

If parts are required, ask your dealer for details regarding their availability. If parts are not in stock, they can be ordered before scheduling your service date.

This letter identifies your vehicle. Presentation of this letter to your dealer will assist their Service personnel in completing the necessary correction to your vehicle in the shortest possible time.

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

Customer Support Department General Motors of Canada Limited

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.