Dude you need to jack it up and see where the problem is first.
I had LOOAADDSS of trouble with my gearbox at one stage, between snapping the bolts that hold the starter motor and gear box onto the mount, to actually breaking off a corner of the starter motor, to eventually breaking the mount, it was a feckin' nightmare, but a reletively simple fix in each case if you've got the parts.
Just jack the gear box up, find out what's broken, and replace it.
