I just went through my 83 L52 5spd. I was near being complete and was rotating the input shaft and it was hitting a bump ? A rough spot that physically moved the 4th gear/input shaft away from the syncro ever so slightly. I am completely stumped. I have taken it down and back together multiple times. It has to be something foolish thats more than likely right in front of me. I have attached a video which is far better than my effort to explain it. Thanks in advance for any help.