There is a fault on all transits and most other vehicles once they reach a certain age -- that is the crankshaft pulley has rubber in it ...as a damper . the rubber deteriorates then it separates and pulley can end up falling off.
The tddi part number, that is is early TDDI
1151392
Some i believe did not have this torsional damper pulley, so take a look to see if the pulley is partly made of rubber ..cracking ..cracked , loose or nearly falling off. the rubber is as sort of an insert that is probably a half inch thick or so.
Think you'll need to take a lower plastic guard off .
if not that, then you are taking the auxiliary belt off ..and checking: alternator, steering pump, water pump and belt tensioner pulley for wear and sloppiness and roughness , noise when turning ..if it has AC then you'll also be checking the pump. You'll also be replacing the belt if it looks rough worn or cracked. carefully inspect each unit ..take a good look at them if water pump is failing you'll see crystallised antifreeze near or around its pulley.
see here
https://www.catcar.info/ford/?lang=en&l ... EzMw%3D%3Dall the best.mark