No lights no issues driving. Nothing flashing weird at startup. Got a code reader no issues.I would just get a driveshaft and install it. The rear diffs rarely fail and nearly 100% of the time I hear "bad rear diff" it ends up being something else. It's usually a mis-diagnosis or poor assumption. Granted it sounds like you've got some awaeomse carnage so who knows.
But used diffs are usually really cheap because they never fail so it shoudlnt' cost much. There's no good way to rebuild these - you might as well just get a used one and be done with it. Like i said they almost never fail so just do what's cheap and simple here.
They typically don't drive normally without the driveshaft, that's odd. Cutting or giving (year dependent) power to the Duty C and "lock" it in 4WD which without the driveshaft installed makes it a useable FWD vehicle. I wonder if someone did something.
Does your AT light flash 16 times at start up or otherwise show any check engine or dash lights at start up or driving?
Driveshaft is still there just cut off after the center hanger. It spins up to there.