This has been a long time coming, but the NHTSA has finally launched an investigation into the manual transmissions used on 2011 and 2012 Ford Mustang models. The agency has received 32 complaints to date, including both 5.0-liter and 3.7-liter equipped cars, but the issue has been well-documented on Mustang internet message boards for nearly a year. There may be 32 official complaints, but there are a lot more dissatisfied owners out there.
Those experiencing problems report a difficulty in shifting into gear, especially first gear or third gear. Sometimes double-clutching helps, while other times it has no impact. Several owners complain that the problem is worse when turning left, while others say it occurs when pulling onto the highway (with the transmission under heavy load). One common denominator is this: the problem only occurs when the motor is running, and the transmission shifts just fine when the car is shut off.
Ford has yet to issue a TSB on the matter, and their response to customers seems to vary by area service rep. Some owners have had repairs done under warranty (with no luck in fixing the problem), while others have had warranty claims denied under the “they all do that” excuse. Now that the NHTSA is looking into the matter, the good news is this: if a problem is found, Ford will be obligated to fix it.