engine speed related vibrations
 

i could feel a vibration on my cummins isx 500 @ 1300-1450 rpm (978K miles). i know it's not my drivetrain. i would put it in neutral and rev it up to around 1300-1450 and could feel the vibration, kind of like when the driveshaft needs balancing.

anyone know what the cause could be? any advice would greatly be appreciated....

At that mileage there's a good chance that the harmonic balancer (also sometimes called the vibration damper) needs to be replaced with a new one.

If that's the case, then get it taken care of soon, as that vibration can eventually cause a broken crankshaft.

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I second the harmonic balancer... I replaced mine from Pittsburg diesel. Check out their website and scroll halfway down for it.

The Pittsburgh Power N-14E Cummins and 3406E Cat Electronic Upgrade Kit

:bow:

Yes, definately get that balancer checked out. You could end up with a busted crankshaft and thats some MAJOR bucks.

I experienced this on my way from Chicago to Cincinnati today at around 70 mph, I'll check that out, although my mileage is alot lower then his.

In neutral? ...and it does the same with the clutch pedal depressed and at the same speed?

You're SURE it's not misfiring at that speed?