Well, if I tried running an engine on water instead of oil for a few miles, it'd rattle like a witch doctor.......
Atik, I'd be inclined to have the box off and pull it apart. If you're stripping the car anyway, you've got nothing to lose but the price of the labour. If you decide to put another box on, you'd have had to have done it anyway.
As has been mentioned above, I wouldn't break it for a gearbox failure....you've got all the unknowns fo a new car otherwise....which may do exactly the same thing 5 miles down the road!!!