Some 2005-07 4.0L Mustangs with manual transmissions may produce a knocking or rattling sound under light acceleration.
According to Ford, the noise is most obvious in 4th gear, with the engine between 1800-2200 rpm and the vehicle speed at approximately 45 mph. A resonance condition in the powertrain is the most likely source of the noise.
The fix depends on when the car was built. For vehicles produced on or after Dec. 4, 2006, replace the flywheel with an updated design, Part No. 8R3Z-6375-A.
For vehicles manufactured before Dec. 4, 2006, install the new flywheel along with an upgraded clutch disc and pressure plate, Part No. 7R3Z-7550-B and 7R3Z-7563-B, respectively.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].