My 2003 F-150 5.4L V8 Supercrew has recently developed a new hum/vibration. It can be heard well and is felt through the steering wheel/column. I can't seem to figure out why this started but I've noticed that when I accelerate to 65 and release the gas, the tachometer doesn't drop rpms as fast as it usually did. When below 30 MPH it doesn't make the new noise but when I merge onto the highway it sounds clear. Recently I've had my number 4, If i remember correctly, spark plug replaced after having an issue and had my driver front bearings replaced.

I'm not sure which direction to take to solving this issue. I've removed my air filter to see if its too loaded with dirt, but still seems clean.

Any help will be much appreciated. I've had this vehicle for quite some time and I don't want to see anything happen to it that I could've prevented.

 

Does anyone think it could be transmission related?

 

Clean your MAF, throttle body and IAC valve. We'll start there and see if it could be air related. Also, change the rest of the plugs.