Terrible Rattling Sound Until 1400 RPM

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CollegeCummins

Who Brought the Cooler?
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Mar 21, 2011
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I am asking this question for my roommate. He has a 99.5 Super Duty with the 7.3 and the ZF-6. He put in a Valair DD Clutch this weekend. It was running fine until yesterday morning then it started making a very strange noise. At idle and lower engine speeds it is making a terrible rattling sound. If he drives it the rattling suddenly stops and the truck is very quiet (Stock noise levels) as soon as the engine hits around 1400 RPM. It is like someone flipped a switch and the extremely loud rattling instantly stops. As soon as the RPM's drop back below 1400 the "switch" is flipped again and the sound comes back. The rattling occurs whether the clutch is pushed in or let out. It does not matter if the truck is moving or stopped. With the truck stopped he can free rev to about 1450 before the sound goes away. It is also difficult to shift into and out of gear. After the new clutch was installed the truck shifted perfectly. Almost no effort was needed to move the shifter. As the noise has gotten worse so has the shifting. It is now to the point where it has to be forced into and out of gear. We have checked everything we can think of, all fluid levels are fine and the exhaust and any other components that could be loose seem to be tight. We need some help. We are completely out of ideas. Any suggestions will be helpful. Thanks in advance.
- Jon
 
Could be a throw out bearing. I would give Dan or Heath a call at Valair and go over some of the characteristics you're dealing with and take it from there. They're stand up guys and will help you get your problems sorted out. Hopefully it's something small.
 
Have the flywheel bolts worked loose? That sounds exactly what a loost flex plate sounds like. You could pull the starter(if there isn't an inspection hole) and see.
 
My guess is the fork and pivot, but a throwout bearing that has come apart will make a similar sound. Had that happen on a Kenny's single disk in a 6.7 dodge, ***** rattled from the moment we started it up, but it went away when you pushed in the clutch.
 
That's why I asked.. the old ones were weak.. they have a newer updated one now. If that's the problem hopefully it didn't take out the throw-out bearing or sleeve.
 
zstroken said:
Have the flywheel bolts worked loose? That sounds exactly what a loost flex plate sounds like. You could pull the starter(if there isn't an inspection hole) and see.
Click to expand...

this, on the autos anyways thats what it does when you crack a flex plate
 
Gabe talked to Dan at Valair and he suggested a lot of the same things you guys are talking about. The fork is brand new but we are going to pull the slave out and see if there's any movement in the fork anyways. We will pull the starter and check the flex plate while we are at it. Is there any way to check the throwout bearing without dropping the whole tranny? Dan if you read this, thanks for your help. We'll let you know what we find.
 
Is the noise stopping or constant John? And are the bellhousing bolts still tight? Did Gabe get the starter all the way tight? And have you checked the stellar exhaust yet? Could be that damn heat shield hitting the downpipe as well. Give me a call after 10 tonight or txt me anytime.
 
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