At higher rpm's I get a bad chatter sound. Replaced the tensioner pulley but didn't fix anything. Hard to tell exactly where the noise is coming from because the 4.0L is pretty loud at high rpm with the fan blowing and everything. Anybody have any clues?

Take the belt off and see if it still makes the sound at start up.

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2021 F150 5.0 Screw

Past:18 F150 2.7, 16 F150 5.0, 14 F150 5.0, 07 F150 5.4, 03 Ranger 4.0

Master Certified Ford Parts / Warranty Admin

You are probably experience the timing chain rattle.

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. It doesn't make the noise at startup

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. That's really a possibility? If that is the case then I'm just going to have to live with it. I'm not doing a timing chain just for a little noise

Is it a squeak type noise or like something metal

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2017 Lightning Blue Mustang GT PP 430/402
CJ Pony Parts Lowering Springs | Texas Speed Longtubes | PMAS CAI | Lund Tuned | Borla S-Type Catback
2013 F150 FX4 5.0 - Sold
1998 Jeep Wrangler TJ 4.0 5spd - Sold
2001 Mustang Bullitt - Sold
2005 Level II - Sold
2001 Integra GSR - Sold
1999 XLT - May 2013 TOTM - Totaled

Replace the tensioners and see if it still is there. If it is, you're SOL.

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^^^ tensioners are fairly cheap and replacing them isnt too difficult.

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2017 Lightning Blue Mustang GT PP 430/402
CJ Pony Parts Lowering Springs | Texas Speed Longtubes | PMAS CAI | Lund Tuned | Borla S-Type Catback
2013 F150 FX4 5.0 - Sold
1998 Jeep Wrangler TJ 4.0 5spd - Sold
2001 Mustang Bullitt - Sold
2005 Level II - Sold
2001 Integra GSR - Sold
1999 XLT - May 2013 TOTM - Totaled

It's not a squeak and it's not really metallic either. It's sounds like a bad pulley or bearing

I have seen the AC clutch bolt loosen up causing a rattle.

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2003 Ford Ranger XLT-2.3L, 5R55E Trans, 7.5 Open Diff

Remove the belt and check the pulleys

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2017 Lightning Blue Mustang GT PP 430/402
CJ Pony Parts Lowering Springs | Texas Speed Longtubes | PMAS CAI | Lund Tuned | Borla S-Type Catback
2013 F150 FX4 5.0 - Sold
1998 Jeep Wrangler TJ 4.0 5spd - Sold
2001 Mustang Bullitt - Sold
2005 Level II - Sold
2001 Integra GSR - Sold
1999 XLT - May 2013 TOTM - Totaled

I did and the only pulley with play was the tensioner. I replaced it and it still makes noise

Take the belt back off and spin all the pulleys and listen real close for any noise. Just cause they don't have play don't mean its good. If the bearing gets dry you get a noise then play..

All pulleys seem good. My understanding is that there are 3 timing chain tensioners on the 4.0 sohc motor. Two of which are for cold start and then work off of oil pressure once it warms up. Seeing as how my problem is at a certain rpm range is it safe to rule out these two?

If the tensioners aren't holding oil pressure then that can also be a factor.

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