Annoying exhaust vibrations at idle

[JGoss]

My 04. 5 's exhaust has vibrated like carzy since new. It only does it at idle. It cracked most of my hangers and ruined my stock exhaust so I got fed up and bought the 5" magnaflow system and know it's starting to do it. I crawled under the truck a few weeks ago and it cracked around the entire weld of the exhaust hanger near the back. My mirrors vibrate so bad they won't focus when at a stop light, everything is blury. The exhaust is pushed together and the clamps are all tight. My truck runs fine and I have no other problems except at idle. Has anyone heard or seen this??

 

[cerberusiam]

Ummmm, if your truck is vbrating so hard the mirrors shake and its breaking the exhaust you have some serious engine issues.



Is this an engine vibration that comes and goes with rpm or ??? The engine needs to be isolated from the frame with all the mounts good or it will transfer. The same with the exhaust, everything needs to be isolated on the mounting points.



Even with all that if exhaust welds are breaking, it has some bad juju.

 

[edgeman]

I wonder if it has something to do with the harmonic balancer on the front of the crank shaft? Just a thought.

 

[JGoss]

The engine runs fine with no vibrations other than normal. I have unhooked the exhaust beside the transmission and that seemed to stop most of the vibrations. I was thinking more along the lines of the rubber hangers the connect the brackets on the truck to the hangers on the exhaust being wore out. It seems the holes are kind of oval shaped but there is still some tension on them. Just thought maybe others had issues too? Do the rubbers have to be there or can I do something different?

 

[steved]

The engine runs fine with no vibrations other than normal.

Define "normal"... what you may think is normal may be abnormal. That amount of "shaking" isn't normal by any means.



One other thought would be that the exhaust was installed in a "bind" and isn't free floating?

 

[JGoss]

Between my family and I, we have 6 3rd gens on our farm. They all run and feel the same except my exhaust vibrates way more than theres. So no the engine does not vibrate just the exhaust.

 

[cerberusiam]

When you bring the engine up off idle does the vibration change or go away?

 

[JGoss]

Yes, only at idle does it do this. It smoothes out once it revs up. I'm pretty sure it's the exhaust and not the engine b/c it runs fine. Like steved said, maybe it's in a bind, but i've had the exhaust apart and then put back together using the u-bolt style clamps instead of the band clamps that came with the system. The exhaust is extremely heavy and I'd bet that if something is a little loose and starts to vibrate it only gets worse, but why does it do it at idle and no other time??? This is not a serious problem, but very annoying.

 

[steved]

... but why does it do it at idle and no other time???

Probably just at a resonate point. When you rev up; the resonate point moves.

You wouldn't think that either the cat or the muffler are broken internally would you?? If the muffler baffles are broken or parts of the cat have blown into the muffler, it would rattle. FWIW, I have a 94 1500 do this... they dropped the Y-pipe on the ground when they replaced the transmission, breaking the catalyst apart... a little bit later and the pieces were rattling in the muffler... sounded like a loose heat shield.

 

[cerberusiam]

Yes, only at idle does it do this. It smoothes out once it revs up. I'm pretty sure it's the exhaust and not the engine b/c it runs fine.

The exhaust just amplfies what the engine is doing, idle or otherwise. If you have enough vibration at idle to rattle the mirrors that is not right.



If you don't mount the down pipe to the trans with a support, the weight and harmonics are going to kill the exhaust system and eventually break the down pipe. If removing that helps you have an engine problem somewhere.



Unbalanced injectors can and will cause an idle harmonics that will rattle the exhaust apart. An unbalanced turbo will do the same thing. If you have as many other trucks that don't do this then you have your answer, that engine has a problem somewhere.



It may run fine off idle and even look like its smooth at idle but what you describe is abnormal. If all your drive train mounts are good the engine has to be the source.