Did you take the starter apart and clean it and lube it? If you greased the helix on the starter shaft, it will collect dirt and not allow the pinion gear to move far enough into the ring gear causing a grinding noise and not turning the engine over. The helix should only be lubed with dry lubricant. Also, there are shims between the solenoid and the starter housing. If you lost the shims, you might get the same result.