About 70% of the time when I start my 2014 it is absolutely silent, so I have to check the screen to make sure it is running. The rest of the time there is a rumbling/growling noise that sounds like it is coming from right front of engine compartment. Two different Ford tech guys say the sound is normal, depending on weather, etc. It only happens the first time I start, after running and shutting off, it is silent. Usually it goes away quickly, but yesterday it continued for several minutes. "Coasted" down the road for a couple of blocks until it was silent. On a few occasions it did start silent, but shortly the noise began. First hybrid I've owned, so pretty clueless about this. If there was a transmission fluid dipstick I would check that. Any suggestions?