I drive a '10 AT sport. Anyone have any clue what is wrong with my car?

For the past 3 months or so, I've noticed a (bear with me in this description) grinding, churning, hiccup-sounding noise coming from the driver's side engine/transmission/CAI area. It's not so much a high-pitched sound, as it's more on the lower-pitched spectrum.

I only recently started tracking when the noise occurs, and I've noticed that around 2-4 seconds after my car shifts from 2nd to 3rd gear (depending on how fast I'm accelerating), the noise happens. It only lasts for a second or two, and I feel like my car has a loss of power during this time; all other gear changes are normal with no sound/loss of power.

It happens when my car is in the "D" or "S" settings, and seems to NOT make the noise when I accelerate very hard (shift >4000 rpm). I usually accelerate at a speed where my car will shift at, or around, 3000-3500 rpm. It also happens regardless of how cold or warm my engine is, and how cold or hot the outside temperature is. My car maintenance is up-to-date and the odometer reads 30,800.

My only explanation for the noise is that I somehow messed up the transmission or engine with my boredom. That is, I use my paddle shifters when I'm stuck in traffic or otherwise falling asleep on a longer drive home. I know the driver's manual has recommended speeds (mph) for when to shift, but I usually just shift around 3000-4000 rpm. Not sure if this did any harm.

 

It's nearly impossible to mess up the transmission by using the paddle shifters. The car's computer won't let you shift when it would be harmful, paddle or not. Shifting at 3000 or 4000 rpm is perfectly reasonable, too, not even worrisome. (It may not be ideal for gas milage, but that's a different story altogether.)

As to what the noise is, I can't say I have much idea. Perhaps it's related to the torque converter lock-up mechanism engaging. Some here have said that changing the ATF helps these sorts of things, and isn't a bad idea regardless to get the maximum life out of the transmission.

 

+1 for doing a transmission ATF drain/fill.

I had this around 30K miles and described the noise as "fluid being released under pressure" lasting perhaps a second during shifts from 2 to 3. It occurred when the car was still cool (less than a mile after starting). A drain fill with Honda's newer spec DW-1 ATF cured it. It now has 65K with no recurrence. As a safeguard I've opted for 30K ATF drain fills. Honda doesn't call for it until sometime after 100K by the maintenance minder. It's expensive at Honda and an easy DIY. Check prices. Honda shouldn't charge more than $70 as it only involves draining 3 quarts of fluid and refilling. DW-1 is about $12/quart.

Many here have had a similar experience. I've only heard of one person getting work done by Honda (torque converter replaced).

 

Glad to know my paddle shifting shenanigans didn't do anything. It was recommended to me by a friend to change the ATF as well, but I didn't think the sound was a "fluid being released under pressure" as much as it was a metal grinding noise. I'll see if it sounds like that over the next week or so until I have time to change the ATF myself. Thanks for the reply you guys.