No crank no start

[jagerwhal]

I'm having a problem diagnosing a engine or trans problem. I have a no start and no crank. I can rotate the engine backwards by hand but it is instantly locked trying to rotate forward. Any suggestions?

 

[Papasonic]

What happens when attempting to crank engine? Does starter attempt to engage; does it appear to engage but won't turn?
Starter shift mechanism may be stuck, and starter clutch pinion may be engaged with flywheel; causing engine to lock one direction, but turn in another because of the one-way clutch within the starter drive mechanism.
Another cause would be a hydro locked situation; liquid/coolant in a cylinder, but I believe that would prevent rotation in either direction.
We need a few more clues to work with, as to what happens when attempting to start.