m1028 engine making noise it is not suppose!

My 86 m1028 is making some roaring noise in engine that diesels are not suppose to make. When at idle or in neutral it makes the noise. When in gear and excelerating it goes away untill just after it shifts then goes away again untill it gets to speed then it comes back. I have checked compression in all cylinders which are ok. I have been told to pull the valve covers and check for broken rocker arms. Sombody else told me it maybe a cracked or loose flywheel. HELP anybody that has had this problem before please. Thank You

I WOULD CHECK THE FLYWHEEL. Sounds like a cracked or broken flywheel for sure, how do i know, the company worked for i drove a ford van with 7.3 international diesel and it did the same thing i drove that thing all day long like that and you could hear me coming a mile away, thats what the mechanic said when i stopped in to see if they could tell me what was up...

Sounds for sure like torque converter or flex-plate. Not uncommon for the flex plates to crack.

I have a spare flex-plate if you happen to need it.

You guys hit the nail on the head. I seperated the torque converter from the flex-plate and no noise. I thought my problem was in the torque converter. After pulling the transmission out i found cracks between every hole in the center kind of like connect the dots.<img src="emoticons/icon_smile_big.gif" alt="Big Smile"> I found a flexplate for a 6.2 with a t400 hope it works ok?