Coles Notes: Tranny will grind and/or feel clicky.
Your synchros need friction to equalize the speed of the driven shaft and the layshaft so the teeth can engage the gear. If I was still rebuilding transmissions I'd snap some photos for you to show what happens to the teeth when they don't synchronize enough (sometimes through driver abuse too). I'm sure you can find this on howstuffworks.
-Michael
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