2008 RAM 2500 6.7L Cummins - Bad Vibration/Shake?

08 6.7L with G56, DRD tuned.

Cross-country trip SOON.

It suddenly developed bad vibration.

It's worst at idle while sitting still in neutral but there through all rpm ranges.

There is no correlation between motion and speed.

It seems worse under a light load but goes away under a heavy load and higher boost levels.

I can feel it when the motor turns over before it fires, and the shake at shutdown is highly exaggerated.

The truck seems to run and sound completely normal other than a slight drone in the exhaust note that stated simultaneously.

Things I've checked:
Valve Lash
Motor Mounts
Harmonic Balancer

I borrowed a matco diagnostic tool and did an injector kill test.

Everything seemed normal there, but all ran a fuel system check which failed in several steps but gave no explanation on what exactly was being tested or why those steps failed.

I am lost on what else to check; any idea or insight is greatly appreciated.

I have a trip from SC to TX in a few days, and I dont want to grenade anything or be left on the side of the road.

Odd, it sounds like you have already checked the apparent suspects; motor mounts would have been my first guess.

Have you noticed any correlation between the vibration and exhaust pressure pulses at the tailpipe?

Yes, in the sense that it corresponds with the rhythm of the motor.

Not up to speed on the Gen 3 G56, but wondering if you have the dual mass flywheel?

It kind of makes me think it has something to do with your clutch or your flywheel being a little loose or warped.


2016 Ram Laramie 3500, G56, 6.7, CC, 4x4

No, I should've included that in my original post, but it's a solid flywheel with a Valair dual ceramic clutch.

When has the fuel filter been replaced?

Yes, with a plugged filter, a bad vibration clicks in my head.

If what you have checked tallies out, what I would suggest, is to look at the fueling.

CP3 A\D, injector rates, filter, and or plugged lines.

Have you been running any fuel additives?

With the scan tool, no codes have tripped.