X15 tractor vibrates when engine brake is on

[Chamberpains]

Is this thing tuned or demandated in any way?

I saw in your other posts that this truck is taken to a Peterbilt dealership to have work done. This could be your problem right here. There are hundreds of people on here that nothing but horror stories about how a dealership screwed up.

If I were you, I'd get on https://quickserve.cummins.com/info/index.html and register your engine for free. Start learning how to run the overhead adjustments on that exact engine, gather a few tools and start checking things out with your own eyes.

Dealerships are ripe with big headed bafoons that think they know it all and yet screw up every procedure in the book or take detrimental shortcuts. All because they got a little bit of training, that they probably didn't take seriously or listen to fully.

If you value your business and that truck, then start getting dirty and getting hands on with it. Now-a-days it's the only way an O/O can survive. Dealerships will bleed you dry real fast. Leaving your equipment broken and you broke. They won't give a damn when you cant feed your family or take care your responsibilities because they were to inept to do a job right.