Some techs have had complaints of a whining noise in customers’ 3.5L GM engines. This whine or rattle noise that occurs on light acceleration and may be more pronounced at start up or after an overnight soak has been reported on 2004 GM 3.5L VIN 6 engines. The source of the noise may be an interaction between the balance shaft chain and the tensioner. There are two balance shafts in this engine that are driven by the crankshaft to keep the engine running smoothly. This noise may vary from vehicle to vehicle, but does not cause any durability concerns.
To cure this problem, GM has designed a new tensioner to eliminate the noise. The tensioner kit, P/N 89017543, consists of oil-fed tensioner, longer tensioner bolts, balance shaft drive chain and right side balance shaft assembly. Please note that it is necessary to install the updated balance shaft assembly because it contains an oil feed passage for the oil-fed tensioner.
This new tensioner was introduced into production in the mid-December 2005 time frame. If the customers’ vehicle was built prior to VIN breakpoints 48123220 (Chevrolet) and 48123225 (GMC), installation of the new tensioner kit is recommended.
Source: General Motors Corp.