Need Help Diagnosing

[skuph]

I just got my ka rebuilt and i went to go get a smog check as i was pulling out of the drive way i heard a loud grind trying to reverse . I immediately shut the car off, started it a couple minutes later and no noise so i took off as i was driving i noticed a bit of a grind shifting in between gears, i pulled up to the station and the grinding began again so i pulled into a neighborhood and parked.
I'm stuck on what this problem could be, any ideas? i didn't have this problem before my engine got rebuilt and the clutch was still in decent condition.
The car will go into gear while off but once i turn it on it will grind going into gear and also while i try to drive it. any help would be great.
I apologize if this has been covered already but i haven't found a thread on my exact problem