Originally Posted by Spike555

Engine, trans, t-case, drive shafts, diffs, axles are all connected in that order.
When you put the trans in park you lock the trans with what is basically a ratchet gear to keep it from turning.
Lock the trans and the t-case wont turn either, because the output shaft on the trans goes into the input on the t-case, so they are locked together.
If he has a blown diff it may still roll while in park.
If the t-case is bad it may roll while in park.
If the trans is bad it will not roll while in park unless the parking prawl is broken.
Put the t-case in neutral and you can have it in park and push it down the street all day and the trans will not make any noise because with the t-case in neutral it is completely disconnected from the trans..
Strip the gears in the t-case and it is in effect disconnected from the rest of the drive line depending on which gears strip etc.
He said while in gear and the engine running and foot off the brake non of the drive shafts move, so either the t-case is in neutral or it is bad.
If it was a blown diff then the driveshaft that went to that diff would turn but the truck would not move.
As I already said the reason his trans makes noise when he puts it into park with the engine running is that the gears inside of the trans are moving, they think the truck is idling along because they are spinning, remember that the engine turns the trans then the trans turns the t-case.
So if the trans is turning then you put it in park it will make that ratcheting noise, that is the parking prawl trying to lock into park.
The reason this happens is that with no resistance on the trans all of the gears inside it will move because they are under power from the engine.
What he needs to do to stop that is shut the engine off with it still in gear, then put it in park.