833 OD sticking in 4th, chipped synchro

I've been reading your post with great interest as I have the exact transmission and problem as you describe. After 20 years of trouble free driving yesterday my transmission locked up in 4th gear after cruising on the highway. It freed up and worked normal until I got back on the freeway and it locked up again. I haven't torn into my transmission yet but would really like to know what you replaced and the results. Where did you purchase parts Brewers / Passon or ? Can you advise if the new Keys and synchro solved your problems?