I've got a D15 cable transmission that I replaced the input shaft bearing in about 3 1/2 years ago. Seems to be making another noise that is very similar now. It's been getting louder and louder recently (sounds like the ISB again). About two weeks ago it got stuck in 5th gear and I had to pull it out of gear with all my strength. Everything was fine after I got it out. Happened again but this time with 1st gear. After pulling it out of 1st, I no longer had 5th gear. I can try to push it into 5th gear but it grinds like there's no synco there at all or the syncro spring is missing. It some times won't catch at all.. just grind like crazy. However, I can usually manage to get it into 5th if I rev match and hold it in gear while on the freeway. If I don't hold it in gear, it'll just pop right back out when I let off the gas.

Question is.. Does this sound like a rebuildable transmission? I've never replaced syncos before. Could the ISB or other bearings be causing this to happen? TIA