I have been trying for two years to educate myself to help me diagnose my gear grinding in first and reverse without actually pulling the trans out which I know is a difficult if not impossible task. I have a 901/13 with AFMSZ gears. Shifting into first or reverse is quite a bit easier upon startup with colder/ thicker gear oil viscosity. In fact my shifting is much smoother in the winter than the summer. Double clutching seems to fix the issue especially when downshifting. My understanding is that my syncros are crush style which requires more friction than other types of syncros so the syncro can come to the input shaft speed to engage corrctly and/or quicker. Double clutching seems to accomplish this. My 2,3,4 and 5 gear do not have the grinding issue but they also downshift much easier when double clutching. I have checked my clutch cable for stretching, adjustment and the pedal stop and they are all adjusted correctly. I am using Kendall gear oil. My questions are, is this a sign of syncro failure or an input shaft lubricating issue? If syncro failure wouldn't it be difficult to accomplish smooth shifting even when double clutching? Will an input shaft seal create a similar issue due to a failure in lubrication. I have changed my gear oil twice in the last two years with no noticeable change. I'm just looking for a bit of education as to how the syncro actually works when it is apparently moved and needs to come to the proper speed to engage the input shaft. Any guidance and/or recommendation of some literature for explanation would be greatly appreciated. Again, I cannot engage first or reverse without a bad grind unless I touch another gear syncro or upon a cold start. Infact, I have a delay in clutch disengagement when approaching a stop especially when it's much hotter which has scared the shit out of me as it feels sometimes like I'm gonna rear end the car in front of me for a quick second then disengages.

Thanks,

Bob