X15 efficiency idle vibration

[newyorktruckah]

Hello everyone have a 2019 t800 with a Cummins x15 efficiency 500 with an Allison 4500rds. Truck idles at 600rpm from factory currently around 45k miles. I am having an issue with a heavy vibration at idle and when truck is put in neutral, drive or reverse. It’s shakes so bad you can’t make anything out in the mirrors, we do a lot of paving and my driver can’t make out hand signals from the spotters when slowly trying to reverse. I attached a slow mo video so you can see just how bad it shakes the ps reservoir. The engine mounts are good the trans has a type of transversal leaf spring which was missing the Teflon spacers which has been corrected. I am now starting to suspect that maybe the harmonic balancer has gone bad. Truck was parked for about a year in between it working started occasionally to shuffle around the yard. I am suspecting that the harmonic balanced might have internally become stuck or something to that effect. Let me know what you guys think could be the cause. No check engine lights or anything pulls great and smoothes out once comes off idle but will vibrate again if the engine lugs around 1450 rpm pulling a hill. Have a c15 in a 20 year old T800 and feels like a Mercedes v12 compared to this thing.
Thank you everyone!

Link to video

https://www.dropbox.com/s/9gtgqerr1gcdwe...6.MOV?dl=0