I just got home from driving my 96 ES through hilly, snow covered roads, most of the time in 2nd gear at speeds under 30 MPH. I decided to pop the hood after parking to make sure I still had sufficient windshield washer fluid, when I noticed an odd noise: 3 seconds of a low "warbling" vibration, followed by 3 seconds of silence, 3 seconds of warbling, and so on. I've never noticed this before (it was very hard to hear once I closed the hood. Any idea what this noise is? I hope it has nothing to do with driving in 2, I made sure the tach never crossed 3000, so I hope it isn't an overheated tranny or anything like that.

Any clues? Should I be concerned?

 

fluids moving through the system "burping" back down from the top of the engine to the bottom.

 

Thanks, OLT