Originally Posted by Kawidad
That brings the interesting question of whether or not you could install the 675's lower first gear for better low speed trail/starting and then could allow you to go with better sprocket choices for highway use.
That is why I checked into the parts between the two transmissions. First gear is integral with the input shaft to the transmission. On the XC it is 16T and on the 675 it is 13T. On the output side first gear is the same number of teeth (34T). The output shaft of the two transmissions is the same part number. This is evidence that the transmissions are very similar (except for first gear).
The parts would cost you $270 for the 675 input shaft and $85 for 675 first gear. You would have to completely disassemble the transmission. I would be willing to do this (I used to work as a motorcycle mechanic), but there is no way of knowing for sure that the parts would fit. I suspect that they would. And of course, it would invalidate your warranty (at least on first gear