Having trouble diagnosing a sound that I believe is related to my acceleration/throttle problem. Problem: When reach various speeds from 25 to 50 mph my car makes a sub-woofer bass sound (best explanation since I can't produce actual sound). But when I tap the accelerator the sound goes away, then randomly comes back depending if I stay at a steady mph. Once I hit 55 mph or higher sound doesn't occur. I thought it was a dirty throttle body and cleaned it thoroughly. My Air intake hose was damaged and I replaced it. My Air filter was dirty and I replaced it with a clean one. However, sound continues. Rpms don't rev high, nothing crazy occurs with the engine. I don't think the accelerator is sticking but I'm not really sure.This sound is driving me nuts mainly because I can't figure out what is causing it, any other suggestions or ideas on what it may be I would appreciate the help. Additional information: I have changed my oil in the past and sound didn't occur until oil level started to drop below 90%.

2007 HAH V6 3.0

 

Change the differential fluid with an oil change?

 

Update: After a month the sound lessened and eventually went away after changing the intake hose and spray cleaning the throttle body.