For 1990-2009 cars

# DIESEL ENGINE SERVICE PISTONS PISTON PINS/RETAINER CHANGE

#### VEHICLES AFFECTED: All 1984 Vehicles Equipped With 5.7L V8 or 4.3L V6 Diesel Engines

The piston pin and retainer have been changed for 1984 model diesel engines. This change utilizes a longer piston pin which is chamfered on each end, along with a round wire retaining ring. To accommodate the round wire ring, the retainer ring groove in the piston has been changed from a square cut groove to a rounded groove. It also contains a pry-out notch. See Figure 1.

Some service pistons now being used incorporate the round wire retainer. Eventually, all service pistons will. Goodwrench engines being produced now also contain the round wire ring retainer.

Procedures for removing and installing the round wire ring are contained in the 1984 model service manuals. The service pistons used in past model engines may contain both designs of retaining rings. It is important to remember that the pistons, piston pins, and piston pin retainers MUST, NOT be interchanged. Become familiar with each component. The round wire ring goes with the pin that is chamfered on each end and the piston has a pry-out-notch. The flat snap ring goes with a square end piston pin and the piston does not have a pry-out notch.

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.