My service advisor got a tech to listen to it. It makes a sort of squeaking rattling noise, really noticeable when the truck is idle in gear. They think that a pulley is causing the noise. He said that when it was loudest the idler arm was bouncing up and down. They looked at the lower pulley (JL 4#) and said that it looked like it wobbled a little. They said that I could bring it in for a warranty claim but I needed to put the stock pulley back on before they could make the claim. I just bought the truck used and don't have any of the stock parts. Anyone have one they are looking to get rid of? I am looking for the stock lower pulley with the cage.
Thanks

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There's nothing wrong with your truck. This sounds like the noise that has been refered to as cavitation.

-Edward

 

I had a similar noise it was the idler pulley failing.. It Shouldnt be jumping under normal conditions...

Doug

 

Now that's a dealer! Keep them on your good side

 

The tech brought up the noise of cavitation, but this is not it. He said that this is coming from lower on the front of the motor not the front of the s/c. I may try to record it so everyone can hear it. I have never really heard another Lightning motor or 5.4L for that matter. It all may be normal. I just know that I have 60 payments to go and don't want to blow it up just yet. ha ha

 

That is exactly what they beleive it is. A pulley bearing that may be failing. So did you get the idler pulley replaced?

Thanks for the help guys!

 

They replaced the pulley on mine.. It was very clear because the sound was in unison with the jumping of the pulley.. From in the cab it sounded BAD.. Like a rod knock or something. There is no way that any mods would cause a idler to fail.. Unless they say that the lower pulley caused it to spin to fast. A 4# pulley caused the idler bearings to fail from over revving ?? LOL

Doug

 

I posted the same topic over on the NLOC board and they showed me this topic which may be related. It shows how to grease the pulley. I may try this first and then take it in if that doesn't fix it.

 

Both my idlers were replaced at 400 miles. Sounded very bad inside the truck. Mine would only rattle when engine was warmed up. No worries.