CAMPAIGN: EXHAUST PIPE FLANGE TO MUFFLER CRACKING

SUBJECT: EXHAUST PIPE FLANGE TO MUFFLER CRACKING

MODELS: 1991-92 GMC Forward W4 Series With Automatic Transmissions

TO: ALL GENERAL MOTORS DEALERS

General Motors of Canada Limited has determined that certain 1991-92 GMC Forward W4 series vehicles may have an exhaust pipe that could fracture. The exhaust pipe could frature in front of the muffler as a result of static loading during engine idle and dynamic loading from chassis inputs.

To prevent this from occurring, dealers will install an exhaust brace repair kit on 1991 vehicles that have not had this done and on 1991-92 vehicles will install a new design rubber mounting.

VEHICLES INVOLVED:

Involved are certain 1991-92 GMC Forward W4 series vehicles built within the following VIN breakpoint:

Year Model Plant Plant Code From Through 1991 W4 Fujisawa 7 M7000028 M7004789 1992 W4 Fujisawa 7 N7000178 N7012669

NOTE: PLEASE CHECK DCS SCREEN 45 OR YOUR V.I.N. LISTING 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 PROCDURE:

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 diis bulletin). The listings provided are for campaign activity only and should not be used for any other purpose.

PARTS INFORMATION:

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

Part Number Description Quantity/Vehicle

97047012 Kit, Repair, Exhaust Brace 1 Kit 1991 (ONLY)

97101823 Mounting, rubber, Exhaust 1 Pipe, 1991-92

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:

Repair Code Description Time Allowance

2A Install repair kit - 97047012 3 (1991 ONLY)

3A Install rubber mount 3 (1991-92)

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:

IMPORTANT: On 1991 W4 models ONLY, the shim and bracket modification described in Procedure I may have already been done per PSB 91-6-502 or it may not have been done. If the shim and bracket modification has not been done, please complete the modification at this time using repair kit number 97047012. However, these kits contain an incorrect rubber mount bracket. You MUST replace the rubber mount bracket in these kits with the new part number 97101823 rubber mount bracket following Procedure II.

Procedure I is to be performed on 1991 W4 models ONLY ff the shim and bracket modification described have not previously been done per PSB 91-6-502. If the modification has been completed previously, then replace the existing installed rubber mount bracket with new part number 97101823 rubber mount bracket following Procedure II.

Procedure II is also for 1992 models which were built with the shim and bracket modification. However, on these units, the rubber mount bracket needs to be replaced with new part number 97101823 rubber mount bracket.

Refer to figures 1, 2, 3, and 4.

PROCEDURE I

1. Disconnect Battery and chock wheels.

2. Install Exhaust Brace Bracket (1) to frame rail on pre-drilled holes and torque bolts to 17 N.m (13 lbs. ft.) (Figures 1 and 2).

3. Install Mounting Rubber (2) to Exhaust Brace Bracket (1) and torque bolt to 13 N.m (10 lbs. ft) (Figures 1 and 4).

4. Install the two piece Exhaust Pipe Bracket (3) and (4) loosely assemble, making sure the Heat Shield is direcdy under the Mounting Rubber (2) and is facing the REAR of the vehicle (Figures 1 and 4).

5. Install the nut and flat washer to join the Exhaust Pipe Bracket (3) and (4) to the Mounting Rubber (2) and torque nut to 13 N.m (10 lbs. ft.) (Figure 1).

6. Torque the Exhaust Pipe Bracket (3) and (4) bolts to 13 N.m (10 lbs. ft.) (Figure 1).

7. Loosen the two nuts off the muffler flange studs, then install the two shims (5) to each side of the studs between flanges (Figures 1 and 3). Torque nuts to 37 N.m (27 lbs. ft.).

8 . Reconnect the battery and unchock the wheels.

PROCEDURE II

1. Disconnect Battery and chock wheels.

2. Loosen and remove the nut, washer and bolt from the Mounting Rubber (2) and the Brace Bracket (1), Loosen and remove nut and washer from stud on Mounting Rubber (2) and Exhaust Pipe Bracket (3-4). (Figure 4).

3. Remove old Mounting Rubber (2). (Figure 4).

4. Install new Mounting Rubber (2) which holds Exhaust Pipe Bracket (3-4) (Figure 4).

5. Torque bolts to 17 N.m (13 lbs. ft.).

6. Re-connect Battery and unchock wheels.

7. Install Campaign Identification Label.

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 deleted.

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.