Strange sound when accelerating

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Jul 30, 2013 | 09:00 AM

Crow27

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Strange sound when accelerating

I've had my 2006 XLT F150 (5.4L) for about a month now and have recently noticed what I can only describe as a 'smacking' sound under my truck when I accelerate quickly. It sounds as if I had something stuck to my drive shaft that is slapping the underside of my truck....except I don't. I don't think that its the timing chain because it seems to be coming from under the cab (between drivers/passenger seat maybe). I hear it most often if I try to quickly accelerate from a normal speed (50mph or so) to pass another vehicle. I do not hear it otherwise. Starts with a 'tink tink' then sounds like something hitting the underside. I'm perplexed at what this could be. Any thoughts?

Aug 2, 2013 | 02:50 AM

renegade734

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Could be a U-joint going bad.

Aug 2, 2013 | 10:33 PM

skunkoffroad

Tuned

Joined: Jan 2009

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Iwe engaging when the vacuum drops during heavy throttle???

Aug 5, 2013 | 08:17 AM

Crow27

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I tried this in 4X4 as well, and it still does it. It's leading me to think its a cat problem.

Aug 9, 2013 | 12:27 PM

BII Plow Truck

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Joined: Aug 2006

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Quote:

Originally Posted by Crow27

I tried this in 4X4 as well, and it still does it. It's leading me to think its a cat problem.

The IWE might not be working while in 4x4.

Aug 11, 2013 | 09:29 AM

Rustynut

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Joined: Sep 2011

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Mine makes that ***** sound as well but I have traced it to a heat shield. But have not had the slapping sound.
Issues with the IWE, fixed for now just a vacuum line off.

06 F150