hissing noise under load - only in 2WD
2006 F-150, 4x4, 5.4, 30,000 miles
For the last two months there's been a LOUD hissing noise coming from my front end. It sounds like forced air from a compressor. Here are the conditions:
1) Only under load - not Park or Neutral
2) Begins under light throttle in any gear
3) Continues if throttle position is maintained or increased
4) Goes away if I let off the throttle or engage 4WD
5) When switching back to 2WD, noise stays gone as long I stay in 4th gear
I've read a ton of posts regarding "hissing noises" but none of them mention the noise going away in 4WD.
I'm under extended warranty, but I really don't want to deal with the dealer telling it's my tires or some other bs. My truck just turned 30,000 miles.