Hey guys,
It's been some time since I posted here. Hope everyone is well. The site still looks great. My 2006 KR now has 37 K miles. It has done some significant towing, but it is running really well. A week ago, a noise developed which is rather dramatic. It sounds exactly as if it is coming from the center of the truck, underneath. It sounds like a tin can filled with little pebbles being shaken. The noise is most evident on exertion. When I get into the pedal a little, it comes on. When the truck is coasting along or not being taxed at all, the nose is not there. Obviously, when there is a boat or trailer on the back, the sound is really strong. The motor is running perfect, the tranny is perfect, there are no leaks, fluid loss or evidence of hoses disconnected.
My suspicion is that there is something wrong with the cats. The location if the sound seems to be right there. Has anyone heard of cats possibly coming apart inside and rattling? They are basically tin cans, and if the guts have come loose, that would certainly sound like little pebbles.
Grady

 

If the noise IS coming from your cats, I think you would hear it with the truck stopped if you reved the engine. But, if you only hear the noise while moving, then it would seem to me to be something else entirely.

You could also just have something loose that vibrates at a harmonic with engine vibration. Something like a loose heat shield or something similar (and I don't even know if there are such things on our trucks - I just know they exist on other vehicles and can make noise).

- Jack

 

Sounds like a loose heat shield to me..

Phil

 

My friend and master mechanic found a TSB on the 4 wheel drive vacuum routing on these trucks. Apparently, there is a vacuum leak which causes the truck to try and place the 4 wheel drive into gear. It does not engage it all the way though, so what you hear is the teeth of the gears slightly engaging. The test? Put the truck into 4 wheel drive and the noise stops immediately. Long story short, the part arrives tomorrow, probably need about an hour to install. Would have been covered by warranty up to 35K miles. I have 37K. Of course this would have to happen this way so I have to eat the bill. Not too happy about this.
Grady

 

Thanks for the follow-up, grady. I'd have to say that I've not read of this particular TSB while on the site but, it's great information to know about it. Once this thread wraps up, I'm likely going to move it up to 'Engines' as it may be a better place to archieve it.

Again, nice post!

-RP-

 

What do bad cats sound like? ..... Meow! Pssst! Psssst! Meow! Hiss! even...

 

OK,
I deserve that one
The rest of the story now. My truck is nice and quiet. 2 hours of labor, real PITA stuff too. These 4X4 trucks have a vacuum system at each wheel which engages the four wheel drive. Used to be, these systems were on the differential hub, but it's different now. When the truck is turned on, a vacuum is created at the wheel which essentially pulls the truck out of four wheel drive. As long as that vacuum holds, the truck stays disengaged and in two wheel drive. When you turn the switch on your dashboard to four wheel, it lets off the vacuum and the wheel engages.
Well, if something happens down at the wheel to interrupt the integrity of that vacuum, the truck will try to engage the wheel. That's what happened to my truck, a vacuum leak. My truck was constantly trying to engage. As soon as the system was repaired and the vacuum was no longer compromised, the wheels stayed disengaged, and the truck got back to normal.
Glad we found it, glad that we could fix it. Not at all happy that this happened at 37K miles with a 35K warranty. Nothing you can do about stuff like this but to eat it and move on but just the same, this is one of those little things in life that make you want to kick something.
Anyway, if or when your trucks start sounding like a tin can full of pebbles, you might remember my saga and maybe this will help some of my KR brothers solve the problem.
Wish you all well,
Grady

 

Grady, that's a HUGE bit of information! On behalf of everyone here, thank you, thank you.

I find this design to be bizarre in the extreme. A "failsafe" mode that puts you into 4WD? Wouldn't it be more logical to require vacuum to put you into the "abnormal" 4WD?

Ah well, I'm not an "automotive engineer" and what do I know?

- Jack

 

Gotta' agree with you. We found it, we fixed it, thankfully we didn't design it. Seemed counterintuitive to us as well, but that's what it was. Again, an interesting proof was that when the truck was rattling away, you could make it stop completely by switching into 4 wheel drive, essentially completing the connection.
Best of Luck,
Grady

 

What part was the fix and how much did it cost you?

 

My cat on my old dodge was toast, and it sounded similiar to what your discribing