ENGINE COOLING FAN DRONE ON ENGINES WITH OR WITHOUT A/C

Some 1988 C/K trucks with 4.3L, 5.0L, and 5.7L engines with or without air conditioning may experience a "drone" noise caused by the fan shroud vibrating. The drone is usually most pronounced at or just above idle. On units equipped with air conditioning, this bulletin applies to only those vehicles experiencing a drone with the air conditioning in the OFF position. If this condition is encountered, it can be repaired by replacing the fan clutch. Use the procedures in Section 6B-Engine Cooling for fan replacement.

PARTS INFORMATION (/ = And/Or) ----------------- Part Number Description Application Quantity ------ ----------- ----------- -------- 22073415* Clutch - Fan C/K 1,2,3 with 4.3L, 5.0L, 5.7L without 1 A/C/KC4/VO1/VO2

22068662 Clutch - Fan C/K 1,2,3 with 5.0L with GU2/GU4/GU6 and 1 KC4/VO1/VO2/A/C

22073409** Clutch - Fan C/K 1,2,3 with 5.0L with GT4/GT5 and 1 KC4/VO1/VO2 A/C

C/K 1,2,3 with 4.3L, 5.7L with GT4/GT5 and 1 KC4/VO1/VO2/A/C

22073403*** Clutch - Fan C/K 1,2,3, with 4.3L with GU2/GU4/GU6, and 1 KC4/VO1/VO2/A/C

with 5.7L with GU4/GU6, and 1 KC4/VO1/VO2/A/C

* P/N 15548580 or P/N 22054876 can be used optionally with P/N 22073415 ** P/N 15550738 or P/N 22008968 can be used opfionally with P/N 22073409 *** P/N 15548575 or P/N 22008956 can be used optionally with P/N 22073403

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.