For 1990-2009 cars

# REVISED DIST. DRIVE GEAR NEW P/N FOR DIST. DRIVE GEAR

#### VEHICLES AFFECTED: ALL WITH HT4100 ENGINES

Serviceman Bulletin 86-641-101 outlines service procedures for vehicles equipped with HT4100 engines which experience abnormal distributor drive gear wear. Those procedures remain valid except that a revised distributor drive gear has recently been released. All 1987 Allantes and other 1987 vehicles beginning with the following vehicle identification numbers (C - 292647, E - 609515, K - 811004) incorporate the revised gear.

For service use, the revised gear is available by ordering P/N 10499813. This new part replaces P/N 10499163 for all applications. The new gear which is constructed from an improved material can be identified by two grooves above and below the roll pin as shown in Figure 1.

WARRANTY CONSIDERATIONS

Previous bulletins on this subject, such as 86-641-101, have described detailed procedures for diagnosis and repair. most important among these procedures is the requirement that when distributor driven gear wear is discovered, the distributor drive gear (camshaft) must also be replaced. The reason for this is that the two gears were together in a pattern and when only one of the pair is replaced the likelihood of a repeat failure i s very high.

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.