2018 freightliner cascadia evo, Pulsating vibration

I have a 2018 freightliner cascadia evo that has a pulsating vibration between 900 and 1300 rpms. It doesn't matter what gear or speed I'm at and seems to get worse as it warms up, it will however slightly diminish if I'm accelerating. I have just over 320,000 on it and I an completely clueless, I've had new steers put on it, new shocks, its had an overhead done, it just came back from being on a dyno and I'm told that it's within warranty specs, but no mention of what or where the problem is or what could be causing it.. but this is clearly a serious problem and if anyone had had something similar or any suggestions I'm all open for that.. Thanks in advance..