File in Section Engin/propulsion System
Intermittent Accessory Drive Rumble Noise During Garage Shift and/or During Parking Lot Maneuvers (Install New Generator with Decoupler Pulley and Accessory Drive Tensioner)
Models: 1997-2000 Chevorlet Corvette.
with 5.7L engine (VIN G - RPO LS1)
and 4L60-E Automatic Transmission (RPO M30)
This bulletin is being revised to update the correction procedure. Please discard Corporate Bulletin Number 99-06-04 (Section 06 - Engine/propulsion System).
Some costomers may comment on an intermittent accessory drive rumbel noise when performing a garage shift and/or during parking lot maneuvers, such as turning the steering wheel to the lock position. This noise may also occur when turning on the air conditioning at idle conditions.
Engine idle speed may drop below 600 RPM while performing a garage shift, turning the steering wheel to lock position, or turning on the air conditioning, This noise may be amplified by a large rate of change in the engine RPM. This condition can also be aggravated by different low engine RPM driving conditions.
A new Generator with Decoupler Pully and reduced damping Accessory Drive Tensioner was implemented for Corvetts with automatic transmissions at 2001 SOP (start of Production). The generator with decoupler pully is used only on Corvettes equipped with an automatic transmission. The reduced damping accessory drive tensioner is used on all 2001 Corvettes.
The new decoupler pully generator and tensioner assembly should be used to service 1997 - 2000 Corvettes with automatic transmissions that exhibit the idle rumble noise.
Refer to the Engine Electrical and Mechanical sub-sections of Engine in the Service Manual for generator and tensioner replacement.
Part Number
10436674 Generator Assembly W/Decoupler  Qty 1
12568181 Accessory Drive Tensioner             Qty 1
Parts are currently available from GMSPO
For vehicles repaired under warranty, use
Labor Operation
J4100     Generator Assembly - Replace - Use Published
                                                             Labor Time

0680      Tensioner, Accessory Drive-          "         "  Replace