Post the serial number of the motor. If it were an alarm from overheat (thermostat sticking or poppet valve) the PCM would put the motor in Guardian mode and reduce rpm's. It sounds like a shift switch fault. If the shift switch sticks in gear or neutral an alarm sounds at 4,000 rpm's. Not all year models are the same but if I can run the sn#, I can tell what rpm the alarm will go off. You might need to go to a dealer and have them hook it to the computer to verify the alarm.