Eaton 18 speed rattle noise

18 speed eaton.
Have had the truck for 2 years now and has had the noise since i got it. Just thought its time to start thinking about addressing it soon. Who knows how old the clutch is, so whatever i do, its preventative and ill obviously throw a new clutch and flywheel and pilot bearing in.
Heres info and i know 100 percent its transmissioon and the rest of my driveline is in tip top condition.
When you let the clutch out and coast at idle in low gear or first you can hear what sounds like marbles in a can rattle. All the way up to the shifter. I have heard this same noise on several older trucks when they are coasting loaded as well. Comes from the trans. Soon as you give it fuel, the noise goes away completely. You have to be coasting. It will do it in 2nd or 3rd or 4th so its not gear related.
This to me, points to either trans input shaft, Trans main shaft, pilot bearing OR maybe the clutch assembly itslef.
There is no debris inside inspection plate and all springs are present in the clutch.
My question is to those who know the noise im talking about, What are your thoughts on what this could be before i take it in a month or 2 or do it myself. Im just to busy to deal with it but it has always bothered me.
Thanks

 

Its mated behind a cat c12. Im pushing around 550hp but that shouldnt matter becuase like i said its been there since i bought the truck. So who knows, it couldve been rattling for 5 years. When i have to coast or let the clutch out, i do cringe. I had noises that shouldnt be there so im looking forward to having trans yanked.

 

this is a strong noise within the trans though. Its there when truck is coasting at idle and throwout bearing is completely disengaged. Noise is not there when you push in clutch and engage throwout bearing. HAs to be load on the transmission to get this aggresive rattle in trans. Sounds like bearings somewhere.

 

sorry. was tired.
I shouldnt have said coasting. I meant clutch out and in gear but not on the throttle. Idling in gear. Basically low rpm and low speed.
Not a ride height issue. My truck is quiet as a bird sailing through the sky in every gear and at cruising speeds. I have all new drivline, new bags and ride height dialed in. This is a issue somewhere withiin the components i listed somewhere. I guess the point of the thread was to see if any one else has experienced this.
Yes you can be in 1st, 2nd, 3rd or 4th but you have to not be on the throttle at all. Soon as you give it some throttle, the bearing noise goes away. Which is what leaves me to believe pilot bearing, input shaft or just a bad clutch disk or pressure plate.
this is a LOW SPEED condition. Rpms have to be below 900 rpm and basically truck crawling.
For example, if you are in bumper to bumper traffic and you just drop the truck down to first and crawl without the foot on the throttle and jut let the truck crawl at idle. This is where you hear the noise in the tans area up through the shifter.
SOry for all the confusion