The last 3rd gear syncro problem post ever!

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Ok, so a lot of people have problems with their 3rd gear grinding, refusing to go in w/out revmatching, or just feeling crappy.

I know I am definitely one of them. I tried redline mt90 (synth 75w90) and it didn't help, 3,000 miles later I swapped it for mobile 1 (synth 75w90) and it didn't help. So I'm faced with swapping trannys or rebuilding. (sr isn't an option so don't bother saying; "just get an sr")

I know a lot of us have troubles with this, so for me and others please help where you can with the following questions.
Note: PLEASE only answer if you know the answer. I have a lot of ideas about the answer to most of these questions, but I'm not 100% certain of any of them really so I'll let the "experts" answer...please do the same. If your one of them...HELP <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>
If you have any questions to add on...feel free! I'd love this to be made FAQ-worthy.

What are syncros?

How do they work?

What causes them to go bad?

Is it my fault?

Is there anything I can do/something I should NOT do in order to save the syncros of my new/rebuilt tranny?

What material are syncros made of?

Can I get them in a different (better) material?

I had more questions but can't remember them...dono how much there is to cover.
So...go at it guys <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>