CAMPAIGN-FLEX PLATE CRACKING (INSPECT/REPAIR PROC.)
SUBJECT: AUTOMATIC TRANSMISSION FLEX PLATE CRACKING
MODELS: 1991 B6/C5-7H WITH GASOLINE ENGINES (RPO LRO AND LSO)
General Motors has determined that certain 1991 School Bus Chassis and C5-7H TopKick/Kodiak medium duty trucks equipped with 6.OL (LRO) or 7.OL (LSO) gasoline engines and AT545 Allison automatic transmissions may exhibit cracking of the flex plate around the bolt circle where it attaches to the crankshaft. The cracking results from excessive stress induced by the misalignment of the transmission centerline with the crankshaft centerline. The misalignment is caused by improper machining of the flywheel housing. The cracking will be made apparent by a noise noticeable to the driver. Eventually, if the noise were to go unheeded, the flex plate will completely separate from the crankshaft resulting in loss of power to the driveline and/or possible transmission damage.
To correct this condition, dealers will check the flywheel housing for eccentricity and replace the housing and flex plate as necessary.
VEHICLES INVOLVED
Involved are certain 1991 B6 School Busses and C5-7H TopKick/Kodiak medium duty trucks equipped with 6.OL and 7.OL gasoline engines and AT545 Allison automatic transmissions built within the following VIN breakpoints:
Make Model From Through ---- ----- ---- ------- GMC TopKick MJ500018 MJ520954 GMC B6 Bus MV500001 MV501905 Chevrolet Kodiak MJ100114 MJ110420 Chevrolet B6 Bus MV100001 MV103725
The specific vehicles involved in this campaign have been identified by 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. Dealers are to correct all affected vehicles in new and used vehicle stock prior to their sale.
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 ensure 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 the name and address of the owner of an involved vehicle was unavailable to GMC Truck Division at the time of campaign initiation, the dealer must 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 Division General Motors Corporation 101 Union Street Plymouth, Michigan 48170
OWNER NOTIFICATION
Owners will be notified of this campaign on their vehicles by GMC Truck Division (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
REMOVAL
1. Block rear wheels.
2. On School Bus only: remove transmission access cover from floor of vehicle.
3. Remove negative (-) battery cable from battery.
4. Raise and support front axle.
5. Drain transmission oil.
6. Disconnect prop shaft at transmission, center support and on school bus only, disconnect the two (2) safety loops.
7. Disconnect dipstick.
8. Disconnect electrical, vacuum, shift linkage connections, and on school bus only, speedometer cable connection.
9. Disconnect transmission cooler lines and retainers.
10. Disconnect parking brake cable and bracket.
11. Unfasten the starter motor from the flywheel housing.
12. Remove access cover from the bell housing.
13. Disconnect the torque converter fasteners.
14. Install transmission jack and support transmission while removing engine mount fasteners.
15. Support rear of engine and remove the transmission case fasteners.
16. Remove transmission.
17. Remove flywheel fasteners and flywheel (flex plate).
18. Perform measurement of eccentricity of the flywheel housing using a dial indicator, refer to Figure 1.
Note: If the flywheel housing is within specifications, continue to INSTALLATION procedures. If the flywheel housing is NOT within specifications, continue to Step 19.
19. Remove flywheel housing fasteners and flywheel housing from engine.
20. Transfer parts from the old flywheel housing to the new flywheel housing.
INSTALLATION
1. Install the flywheel housing and fasteners. Torque the fasteners to 45 N.m (33 lbs. ft.).
2. Install flywheel (flex plate) and fasteners, torque the fasteners to 90 N.m (65 lbs. ft.).
3. Install transmission, align, install fasteners, torque the fasteners to 48 N.m (35 lbs. ft.).
4. Install the rear engine mount fasteners, torque them to 196 N.m (145 lbs. ft.). Remove support and transmission jack.
5. Install torque converter fasteners, torque to 56 N.m (41 lbs. ft.).
6. Install access cover to transmission bell housing.
7. Connect starter motor to flywheel housing, torque to 37 N.m (27 lbs. ft.).
8. Connect transmission cooler lines and retainers.
9. Connect electrical, vacuum, shift linkage connectors and on school bus only, speedometer cable connection.
10. Connect dipstick.
11. Connect parking brake cable and bracket.
12. Connect center support, prop shaft and on school bus only, 2 safety loops.
13. Remove supports and lower vehicle.
14. School Bus only: install transmission access cover at floor of vehicle.
15. Connect negative (-) battery cable on battery.
16. Fill transmission with new transmission fluid (P/N 12345881) to proper level.
17. Remove blocks from rear wheels.
18. Install "Campaign Identification Label".
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 under an advise code (2).
Part Number Description Quantity ------ ----------- -------- 15647398 Housing 1 10114196 Flex Plate 1 462619 Retainer 2 12345881 Dexron-IIE Automatic Transmission Fluid AR
Parts are currently available from GMSPO.
WARRANTY INFORMATION
Dealers should submit a warranty claim on each vehicle completed under this campaign.
Labor Operation *Time Trouble Number Model Description Allowance Code ------ ----- ----------- --------- ----- V7210 C5-7H R&R Flywheel (Flex plate) and Measure 4.3 Hrs. 96 Eccentricity (within specs)
V7211 C5-7H R&R Flywheel (Flex plate) and Measure 4.7 Hrs. 96 Eccentricity (not within specs)
V7212 B6 R&R Flywheel (Flex plate) and Measure 4.9 Hrs. 96 Eccentricity (within specs)
V7213 B6 R&R Flywheel (Flex plate) and Measure 5.3 Hrs 96 Eccentricity (not within specs)
*For dealer to receive Administrative Time Allowance associated with this campaign, add 0.1 hour to the Labor Operation Time Allowance.
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 campaign number and five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or ball point 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 "GM Truck Claims Processing Manual" #P9119.
Dear GM Truck Owner:
Our records show that you own one of our 1991 model General Motors B6 School Bus Chassis or TopKick/Kodiak medium trucks. The rate at which these trucks have been accepted into the stream of commerce has been very gratifying to us. In addition, feedback from customers, dealers, and our own tracking systems indicate a very high degree of product reliability thus far.
We have recently become aware of a situation on certain 1991 B6 School Bus Chassis and TopKick/Kodiaks with a specific transmission which may reduce your truck's reliability. The fly-wheel housing of certain vehicles was machined improperly causing excessive stress in the housing. The stress causes cracking of the housing due to misalignment of the transmission centerline with the engine crankshaft centerline. The cracking will manifest itself by a noise noticeable to the driver. Eventually, if this noise goes unheeded, the flex plate will completely separate from the crankshaft resulting in loss of power to the driveline and/or possible transmission damage.
In interest of maintaining your truck's reliability, we would like to correct this condition by checking the flywheel housing for eccentricity and replacing the housing and flex plate if required. This service will be completed for you at no charge.
Instructions for performing this service have been sent to your GM TopKick/Kodiak dealer. Please contact your GM Topkick/Kodiak dealer to arrange a service date. Refer to your GM TopKick/kodiak Servicing Dealers booklet for the dealer nearest you. The labor time necessary to perform this correction is approximately 4 to 5-1/2 hours. Please ask your dealer how much additional time will be needed to process your vehicle.
The enclosed postage paid own reply card identifies your vehicle. Presentation of this card to your GM TopKick/Kodiak dealer will assist in making the necessary correction to your vehicle in the shortest possible time. If you have sold or traded your vehicle, please furnish us complete name and address of the person you sold or traded your vehicle to and return the card to us.
We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction.
GMC TRUCK DIVISION GENERAL MOTORS CORPORATION
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.
