SPICER CLUTCH CHARACTERISTICS INFORMATION ONLY

SUBJECT: SPICER CLUTCH CHARACTERISTICS

MODELS: 1986-1990 W4, W5, W6, AND W7 MEDIUM DUTY TRUCKS

The following service information describes operating characteristics relating to Spicer cerametallic clutch assemblies:

Clutch chatter can result when the operator starts in a gear other than first (1st), or when the clutch is slipped excessively.

Cerametallic clutch assemblies are especially prone to chatter due to the inherent, high coefficient of friction of the material. Dealer service personnel should educate drivers on proper operating techniques if comments of chatter exist.

Some squeal is normal for cerametallic clutch assemblies, especially before the disc is fully broken-in. Often, over 15,000 miles are required before the full surface of the disc is in contact with the pressure plate. Initially, only the outer diameter of the clutch disc will make contact with the pressure plate during engagement.

DO NOT REPLACE A DISC BECAUSE SURFACE WEAR EXISTS ONLY ON THE OUTER DIAMETER OF THE FRICTION PADS. This is normal for a new clutch disc of this type. (Refer to Fig. 1).

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.