Hoping for any input on a worrisome noise I've been hearing from my 2008 TL base automatic (139k miles).

While accelerating through the gears, a metallic whine/vibration often occurs briefly when entering the next gear. It happens briefly and then goes away. There is seemingly no impact on the performance, and it generally only happens when going up hill, or really getting on the gas such as a highway on-ramp. The noise does not occur in neutral or park, and does not occur if I softly accelerate/take it super gently through the gears, but is seemingly unavoidable when shifting on the highway.

I changed the pressure switches about 10k ago, and just changed the tranny fluid last week.

Any ideas what this could be: tranny, torque converter, other? Heat shields are all fine.

Thank you

 

I should note, the noise began before changing the tranny fluid, and has persisted since changing

 

My son has an RDX that made a weird noise and it seemed to be louder during acceleration. To me it sounded like his transmission. He took the RDX to the dealer and it turned out to be a bad wheel bearing.