After 3 months of searching for a low speed noise under the hood of my 2013 Fusion Hybrid, I think I finally found the source of the rattle. Jacked up both front wheels yesterday and it would reproduce the noise while at idle in Low range. I was able to force the ICE on by turning up the heater while the garage was cold. That let me listen to the engine with a long screwdriver (ear on the handle). Very much louder on the EV housing (HF35 transmission). Made the sound every time the engine caught up with the spinning front wheels.
This noise happens when the ICE kicks in and starts pulling. Lasts maybe a second both when the ICE starts pulling or when it dies or backs off. Sounds like rocks in a can so I had thought it was just a harmonic vibration in a plastic panel or heat shield. I even put microphones taped around the engine compartment and connected them to a laptop in the passenger seat. Recorded the buzz but never could pin it to a very specific area.
I took it to the dealer service dept this morning an got one of their people to ride with me and verify that he hears the noise. Set up a drop off appointment for the 25th.
Just wanted to post this to see if anyone else can hear this rattle in their 2013 hybrid. My 2010 did not have any such noise. Best way to test is to put it in LOW range, turn up the heater, when the ICE kicks in at less than 5 mph, just throttle on and off just above idle to make the ICE start pulling then slack off. At such low speed the noise is easy to hear. Does it in Drive around town every time the ICE pulls or backs off.
I wanted to check the fluid level in the HF35 transmission but could not find the fill hole. Can see the drain plug but not the fill plug. Not like the Prius pictures I have seen. No plug near the drive shaft. I did see a male Torx screw with locknut that may be some sort of adjustment but will leave that stuff alone. Anyway the thought of low tranny fluid crosses my mind and I mentioned that to the service guy.
Sorry for the long post but this noise is really getting annoying.