My problem just started happening about two weeks ago and has gotten a little worse. When i am in drive or reverse the truck has a rattle from underneath the truck that sometimes gets louder almost like something is rubbing against something. When i am in park or neutral the vibration does not occur, and before i take it in anywhere i wanted to see if anybody else had the same problem. Thanks in advance.

 

Is this happening while sitting still? Or, while driving?

 

Its while sitting still.

 

Perhaps your exhaust is rubbing against something. Do you have an aftermarket cat-back?

 

It's really rare, but those symptoms can be caused by a broken motor mount.

 

My exhaust does the same thing, how can you tell its a broken motor mount? why would you come to that conclusion?

 

I do have an after market exhaust but whats weird is when i turned the ac off yesterday it went away but when i turned it on it came back.

 

I had this same problem and I had someone hold the brake while in drive and I got under there to check it out. Low and behold it was a small rock inside catalytic converter shield. I had to bend a metal coat hanger and fish it out. I'm sure its the same thing you have. It's happen to me more than once.

Hope this helps.

 

When you turn on the A/C, the engine idles differently. I would say that's affecting either your exhaust or other components in the engine compartment. Check for the exhaust rubbing up against the body somewhere and make sure your motor mounts are in tact.

 

Thanks for the help guys, I'm going to check i tout this evening and see if I can get this straightened out.

 

The air conditioner, when it turns on, causes a load on the engine. The computer compensates for this by the use of a manifold absolute pressure sensor. It detects an increased load and sends a signal to the idle air control valve to allow more air to go in to the manifold. Hence increasing idle ever so slightly. You will notice a small vibration when the A/C is running because the engine is running different than it is at no-load idle.

 

Well i got underneath the truck and cant pinpoint exactly where it is. I know its up front and when i turn the wheels it gets louder so maybe with me adding the bigger tires and them rubbing it caused something to go bad, idk. I turned off the a/c and it did get quieter but is definitely still there, i may drop it off at ford and see what they say.

 

Perhaps it's the power steering pump or your rack. It's called groan. It's a low rumble that occurs when the steering rack or pump flutters. It can go away or get better when the A/C is on because the compressor and PS pump are on the same serpentine belt.

The sound I like to equate it to is that old movie submarine creak.