NEW DRIVEN SPROCKET SUPPORT AND CHAIN SCAVENGING SCOOP

MODELS AFFECTED: 1990 4T60 (TM 440-T4 AUTOMATIC TRANSAXLE)

CHANGE TO ASSEMBLY COMPONENTS (Figure 1)

A new driven sprocket support and chain scavenging scoop is used in production on 1990 Century, Electra/Park Avenue, Riviera, Reatta, LeSabre and Regal models equipped with a HYDRA-MATIC 4T60 (THM 440-T4 Automatic Transaxle). The new driven sprocket support requires the chain scavenging scoop to be about 1/3 the length of the previous scoop.

IMPORTANT: The new driven sprocket support will service past models, but the new, shorter scavenging scoop must be used with it. The previous scoop will not fit. Do not leave the scoop out. This will cause durability concerns.

Do not use the new, shorter chain scavenging scoop with the previous driven sprocket support assembly. This will also cause durability concerns.

DATE OF PRODUCTION CHANGE

Starting August 16, 1989 (Julian Date 228), all HYDRA-MATIC 4T60 (THM 440-T4) transaxles will be built with the new driven sprocket support and chain scavenging scoop.

SERVICE PROCEDURE

The new driven sprocket support and chain scavenging scoop will assemble the same way as the previous. The previous scoop can be cut to fit the new support. Lay the previous scoop on the actual size scoop in Figure 2 and cut at the line. Smooth off the rough cut edge.

SERVICE PARTS INFORMATION

Part Number Description Model Year ----------- ----------- ---------- 8668385 Support Assembly, Driven Sprocket 1984-90

8668613 Scoop, Chain Scavenging 1984-90* - Natural color for 35 tooth driven sprocket *Must be only used with new support

8651622 Scoop, Chain Scavenging 1984-90* - Black color for 33 tooth driven sprocket *Must be used with new support

Parts are expected to be available on December 30, 1989. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. GMSPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while the 400 control is in place.

SERVICE NOTES

The service part number did not change from the previous to the new driven sprocket support assembly. Either style may be available until the previous style stock is depleted; then the new style support will be the only style available. Cut the previous chain scavenging scoop for the new style support following procedures listed in this Service Bulletin.

SERVICE MANUAL REFERENCE

Refer to the appropriate Service Information Manual for service procedures.

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.