Can you identify this sound? w/audio sample

usa591 · **Posted:** Tue Aug 09, 2011 12:43 pm

Ok amigos, this particular noise has been driving me crazy:

http://homepage.mac.com/filmgroup/perma ... 80811.aiff

...be patient, it's a 14mb file.

You will hear me come to a stop and then it starts--it's really obvious to me at :12 into the file. I EQ'd the same recording to bring out the high-end sound and at :51 you can hear what I'm hearing. You hear the normal diesel cadence and then there's a metallic overtone that phases in and out.

I only hear it at idle speeds, coming off a freeway ramp or stopped. And to me it sounds like something metal rattling around like a loose heat shield--but I checked, and you can only hear it in the cab, not from the outside. I would almost describe it as loose change rattling around... The vehicle runs fine, but occasionally has a shudder problem when coming to a stop and sometimes doesn't shift into Drive when cold.

Any ideas what this sound could be? ....or if everyone else's sound like this, I'll stop worrying about it.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

Based on the fact the noise is most apparent at idle and you cannot hear it from outside the vehicle, it could be a failed engine mount. Does the noise change when the shift lever is moved from D-N-R?

usa591 · **Posted:** Tue Aug 09, 2011 4:28 pm

I believe the engine mounts are ok--my mechanic checked them for me during the last tire rotation. But I will check again.

The noise is constant through P-N-R-D. Also there's no difference with the AC on or off, or when the tranny is in 4WD Part- or Full Time or N.

usa591 · **Posted:** Wed Aug 10, 2011 1:24 am

After doing some more poking around on the forum, I am really curious about looking into the engine mounts & at least making sure they're torqued down right. I see what I can get to this weekend.

camo · **Posted:** Fri Aug 12, 2011 11:04 pm

I bet your mechanic has never even seen the mounts on the libby before. I had that same noise and it was the passanger side mount, If you look at them they look fine but when you take them off and shake them..... yep they sound like a cuban maraca :SOMBRERO:

remove the passanger mount, then take the heat shield off of it and shake it up and down and sideways.... then you will understand why you might want to find a new mechanic.

usa591 · **Posted:** Fri Sep 02, 2011 1:25 pm

Problem solved: it was the engine mounts. I replaced the two engine mounts and the transmission mount. Well, my mechanic did.

When I shake the two engine mounts, it sounds like marbles rattling around inside.

It made such a huge difference--all the weird vibrations in idle are now gone. The vehicle feels brand new.

Cost: $108 in parts and $230 in shop time. Oh, and the spline on the driveshaft was greased--no more thunk.

Can you identify this sound? w/audio sample

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