Vibration/shaking at @1500 under boost.

Trees, that's what the Kenworth dealer that has done all the work is saying, but cummins says that it is impossible seeing as they are internally balanced engines and they recon that if it was a crank it would vibrate all the time even when just free revving, not just under load.
I just replaced the barometric pressure sensor, no change

 

Process of elimination, it is the only thing remaining, although I think that it's more likely to be something with the clutch. A badly imbalanced crankshaft would cause an engine to fail, I'd think, if it was badly imbalanced. Anybody send a used engine oil sample in for analysis? If it was the crank I'd expect to see wear metals way up in a UOA.

 

I'd be checking all the tail shaft angles. If it was My Truck..

http://spicerparts.com/anglemaster/measuring-angles

 

Sorry leftlanetruckin I didn't mean to hijack your thread.

Yes oil samples have been done on engine and gearbox both came back fine. Driveline angles have been checked and the drive shafts have been balanced. It has had brand new friction plates put in and then a whole brand new clutch as well, no change, new flywheel, no change.

I personally think it is fuel. It happens in every gear no matter what speed you are doing, as soon as you put fuel into it and it comes on boost it happens and as soon as you let off it's gone. I actually think that since I have done the barometric pressure sensor that the engine has smoothed out a lot and is running better but the vibration and noise is still there.

If it was driveline it would usually happen at a certain speed not in every gear. The noise from outside the truck seems to disappear at 1800rpm every time, the vibration is still there but the noise goes away. It is very weird. Even 2 cummins engineers that have looked at it are stumped.

 

No problem on the highjack mate, carry on! If anyone else has had a similar issue, chime in.

New clutch didn't solve the issue per say.
It drives better, but it's more hearing it now, than shaking etc.
Injectors have been changed a couple of times now, so I doubt it's them.
Driveline angles have also been checked.
Total cost of a 2050ft lbs Eaton clutch, new bearings and the flywheel resurfaced.......$1037 out the door!

Martin

 

As an update to this....The clutch, although feeling better, did jack to the vibrations.
As a recap, the driveline has been measured etc, so it isn't there. It is also NOT speed specific, only RPM's and boost specific.
Again, 1500-1600RPM's, over 20psi of boost. Clutch pedal shaking and the gear shifter although not as bad.
My local FL shop is now a WS repair shop too, so I swung by there to pick to fuel and oil filters up today. Spoke to their trans guy who said it couldn't be anything inside the transmission, but engine related.
He suggests the turbo actuator is getting confused, and quickly altering boost. OEM boost gauge stays steady, but am tempted to put an actual mechanical gauge into the intake manifold to see if it fluctuates or not.
Another thought was timing or the balancer up front.
Truck sat for @3-4yrs with only very intermittent start ups during that time.
Could it be the balancer up front?
Any thoughts on transmission being a possible cause?
It's under warranty, but they need a place to start so I dont end up with a bill.

Martin

 

Probably not your problem, but an exhaust restriction will cause that same kind of vibration.

 

differential pressure sensors read really good, so doubting an exhaust restriction.

Thanks
Martin

 

Say, like that of a DPF?

 

I have ran an exhaust choked up, and it just didn't want to rev out......This will rev out fine, just that spot of 15-1600rpm's.

Martin