Vibration... need help!

2009 Kenworth
400,000 miles
ISX cm871
13 spd
3.55 rears
I have been chasing a vibration in the seat, floor and pedals for a few months. About $25,000 into it and have not fixed it.
here's the list of everything done to the truck and trailer and it has not changed it:
18 new alcoa wheels and tires (after 5 axles of centrimatics made it worse and spin balancing made no difference)
10 new brake drums and 5 axles of shoes
S-cams, bushings and slacks
Every suspension bushing, airbags and steer axle springs
3 axle alignment and trailer alignment
Engine balancer and all pulleys, belts and tensioners
Flywheel, clutch and all transmission bearings and a few other internals
All 3 axles hub bearings and rechecked the torque 2 weeks later just to be sure
Turbo, egr valve, cross-over, all aftertreatment related sensors
New doc and dpf
New CAC

Not everything is related to the vibration but my point is.... the truck is pretty much new again. I am at a complete loss as to what else can cause the high speed vibration. On or off the pedal makes no difference in the vibration. No engine imbalance codes - injectors test good. No odd idle or power issues. No codes at all.

Anyone have any ideas?

 

Also replaced all 5 u-joints, carrier bearing and had both drive shafts balanced while I had em out

 

When does it vibrate? All the time, at certain speeds, sitting still, coasting, climbing. More details of the problem

 

Smooth idle and acceleration with all the power... vibrates above 60mph under all conditions. Up hill, coasting, heavy, empty....though it is much worse empty. I have dropped into neutral and let the engine idle while coasting at high speed with no change. Every single thing that can cause a rotational vibration has been replaced except for the power divider and diffs... I am getting tired of throwing parts at it and it making no difference

 

Check your ride height and driveline angles.

 

That's a good idea... I will check it out in the morning and update.

 

Ride height

 

Yup^^^^^^

Also measure driveshaft runout.

What speeds does the vibration occur? Is worse on accell or deccell. Worse loaded or empty.

You have already wasted a ton trying to find this. Find a shop with a Eaton DVA and diagnose the issue. Stop slinging new parts.

 

After the vehicle has been driven awhile with the vibration, take a temperature gun and check tire temps, hub temps, around the truck. if something is vibrating it heats up. TA/Petro has a machine that can pinpoint any vibration by the frequency of the vibration. Not at the truck shops, but in their educational training.

 

so, here's where we are.... the drive shaft shop did the runout when they balanced and the overall runout on the front section is 0.0015... mid .0010... rear .0005. They all balanced out. The angles are about 1° up from transmission to carrier bearing, from carrier bearing down to power divider 1° and between both rears 2° down from front to rear diff.

Ride height is about 8.375" (almost 8.5, but not quite) from frame to center of axle loaded and a little over 8.5" not quite 8.675" bobtail.

I will grab a laser thermometer today and start checking temps every time I stop. I am running across the mountains today and the plains tomorrow so I will get temps under different conditions to try and pinpoint a hot spot.

Everything I replaced at this point doesn't bother me as my truck and trailer are paid for and most of it was wish list stuff.... now it's just getting annoying throwing parts at it. I am starting to feel like I have the stealership mentality.... throw enough parts and we will eventually put the right one on to fix it. Blind man in a dart tournament.