9400i clutch or trans rattling at startup

[Chamberpains]

06 International 9400i Cummins ISX cm870

I bought this truck with 750k miles on it and ever since I've had it when you start the truck up the clutch or the transmission has rattled quite obnoxiously for a few seconds then goes away. I've heard many other trucks over the years having the same exact problem (all of them being the 9200, 9200i, 9400, 9400i and 9900 series International) and no one has ever told me what they thought it was or figured it out. All of them just came to the conclusion that it's just what these trucks do when it comes to high mileage.
That conclusion has always bothered me but it's never caused any problems that I know of.

So along the way of owning this thing I have replaced both rear ends and all U-joints, clutch and even threw a whole new engine in it. Transmission has always felt tight and hasn't needed replaced yet. With all of that replaced, the rattling when it started was still there. After replacing the fuel actuators on the engine the problem sort of went away. But not really it was there and came back just like it always did after a while.

Finally this weekend I broke down and replace the vibration damper on the front of the engine (it was supposed to have been replaced with the engine swap. But that incredible nightmare just continues to bite me everytime I think something was replaced or put together properly during that debacle. They simply just painted the old one and put it on my brand new reman engine.) I looked at the damper it looked really rusted and just like it had been on there for 12 years (the crappy paint job finally flaked off). That's what made me finally pull it off and just replace it. And well, what do you know, brand new vibration damper and the god awful rattling upon startup finally is gone. Engine runs smoother without knocking and the transmission doesn't rattle when coasting.

I don't care what anybody says those viscous vibration dampers do dry out and become nothing but off-center counterbalances. I've had guys swear up and down they just never wear out. They can't wear out. There's no way they will wear out with showing that they leak. I can now officially say they're f*ing wrong.

When I get back to the Northeast from my trip down south I'm going to drill into the old one and see if anything comes out. My bet is very little or nothing at all comes out.

Torque specs on the 12, 6 point, 18mm head bolts when installing the damper are 120ft/lbs.
Not impact gun tight! Remember you may have to pull them both back out someday or even worse yet you may have to pay some over priced knuckle dragger $140 an hour to pull them back out. And you'll want to make sure he doesn't spend three hours trying to get the very last Bolt out with every tool in the tool box snapping off..... Use a torque wrench.

No, I did not pay someone to do this for me. But the whole time I was swearing and snapping tools for 3 hours the only thing that kept me going was the thought of not having to pay someone $140 an hour to do this.