I think I have made an error, having just purchased a new XT M771 9 speed rear mech and installed it on a new bike, and I can't get it to shift to 1st and 9th on the cassette. I updated the shifter to the XT M770 9 Speed at the same time but as the cassette was new I didn't change that. I doesn't appear that this mech will reach to the top end anyways, and although I can cope with out the that big gear, I do kinda want that small one back. Would changing the cassette to the XT 9 speed fix this problem??