Stoked

I have developed a vibration that only occurs at idle. It doesn't matter if it is in gear or not, or if the clutch is engaged or not. It sounds like a 12v compressor is running, but I don't have one. If I'm sitting and I can hear the vibration and give it a little throttle, the vibration goes away until it returns to idle. As soon as I slip it in gear, let out the clutch and start moving, it goes away. I can really only hear it in the cab, but it sounds like it's coming from under the hood. If I start it and listen with the hood up, I can sometimes hear it but only faintly. It's really more of an annoyance than anything. I've looked for everything I can think of that could have come loose. I'm out of ideas. Has anyone else had this issue or know what else I can look for?

Names_TJ

tried turning your a/c on and off? maybe your compressor?

elirandolph

mine had a similar sound after I had replaced the muffler. I looked under the truck and one of the hangers that holds up the exhaust was loose. the rubber grommet thing that mates the hanger and the actual exhaust was not under tension causing a weird vibrating sound only in the cab. I bent the rod coming off of the exhaust down a little to where the hanger was actually holding up the exhaust and fixed the problem. Its worth a shot.

Eli

Stoked

Names TJ: I've tried the AC compressor, no effect.

elirandolph: that's an idea. I'll check and see.

2-Stroke

yea, you are hitting the resonate freq. of some component. Have you done any mods recently? I know when I did my stack, I buillt a new exhuast bracket (see gallery) and it sends a little more vibs into the frame than did stock, but goes away off idle. Its not hard welded, so no worries for me... Thats more than likely a probable source.

Stoked

No new mods. It just started about a month ago. I didn't even notice it coming on gradually. I hoped in my truck one night at a restuarant and when I cranked it, I noticed it. Even my wife heard it and commented on it. I had not heard it prior to that. I kept looking for something that may have broken as opposed to just working loose.

N.Johnson

Here's a suggestion, take a close look at your vibration damper (main pulley at the front bottom of the engine). Check the rubber membrane for deterioration or missing segments. There are two scribed lines on the outer member and inner hub separated by the rubber membrane. Those scribed lines should be matching. I would start there and next inspect your motor mounts. How many miles on your rig? Anyway check these out and get back to us we will figure it out and then you can confidently go to the dealer

Stoked

Just shy of 30,000 miles. I'll check the balancer. If that's it, it will give me an excuse for that Fluidamper.

Stoked

The balncer checks out fine. Rubber looks good and the two scribed lines are in-line. I also checked the exhuast system and everything looks tight there.

N.Johnson

Okay now check the motor mounts. Torque on the bolts is 65lbs. Tranny mounts are 35lbs. What I found is after engine breakin allot of my bolts needed to be re-torqued. Another possibility is you have a carbon build up on your injector tips. Had this happen and after a heavy dose of cleaner and a long hard run it smoothed out. You can download the factory manual from hemitruckclub.com

Stoked

The mounts look good, but I'll check the torque this afternoon. I'll also run some injector cleaner and see if that helps.

redspider

yeah run a full bottle of howe's meaner cleaner through your tank and keep the rpm's over 2000. it will go away, had the same thing twice this spring. I could only notice it when sitting at a stop light.