I have noticed this a few times now. Sitting still, idling in neutral, the engine seems to be running rough. Enough to shake the truck and make the gearshift wobble left to right almost an inch in either direction. I can also hear it in the whirring noise the clutch makes spinning in neutral. Only seems to do it, or at least I am only noticing it when the engine isn't completely hot, maybe 150 degrees

 

I had the same problem. The clutch was starting to slip so I took it in to have it replaced. This is when I found out the vibration was caused by the flywheel and the whizing noise was the throwout bearing. All replaced (15,000.00) smooth as new now. The flywheel is spring dampened inside and all that had come apart. Hope this helps.

 

That makes sense. Is the transmission not supposed to whine in neutral? mine has always done it. What I meant was I can hear oscillations in the whining noise that tells me something is not right.

 

sounds like it may be a bad dual mass flywheel

 

$15 grand for clutch work?

Going back to the shop tomorrow, will update.

*edit 10th trip back in 4,500 miles

 

Sorry, $1,500.00 to replace clutch and flywheel