I am modifying the stock TW shaft.
I've noticed the splines on the clutch side are different for the 5-speed and 6-speed shafts that I have seen. I haven't studied closely, but doesn't look like it will be an issue.
Which gears are you using, TT-R or XT? If memory serves, the XT has a slightly lower ratio in 1st and 2nd, but 3rd through 6th are the same for both models. The XT has a 3.091:1 1st and the TT-R has a 2.923:1 first.
Total spread on the XT is 3.091 to 0.793 (3.90), on the TT-R is 2.923 to 0.793 (3.69), on the TW is 2.833 to 0.821 (3.45).
rpm drop in %
........1......2......3......4......5......6
XT......54.6....40.....27....21.5....16.8
TT-R....54.7....32.2...27....21.5....16.8
TW......58.4....35.7...26.7..26.7
I don't complicate the numbers with different primary drive ratios because whatever the ratio with which you end up, the overall final drive ratio is easily adjusted with choice of countershaft and wheel sprocket ratio.
My biggest beef with the TW ratios is the 4-5 gap is too wide. The 5-6 gap of the 6-speed is much more livable, if not a little too close. I've also been a little uncomfortable with the TW's 1-2 and 3-4 gaps, the 1-2 gap because 1st is too low on the street and 2nd is too high, and the 3-4 is just too wide. I'm questioning if the 40% rpm drop on the 2-3 shift of the XT's gears might be a bit much.
Assigning 100 dots equivalent to 1:1 ratio (1st 30 dots removed), here's a graph comparing the maximum rpm shift points:
TW
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XT
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TT-R
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Will you do one for me when the time comes? If so, how much?
Added:
Comparative total reduction ratios if sprockets chosen for same top ratio of engine rpm to rear wheel rpm:
.............1...........2..........3...........4...........5...........6
XT.......3.898.....2.522....1.802...1.418....1.168....1
TT-R....3.686....2.382.....1.802...1.418....1.168....1
TW......3.451....2.179.....1.605....1.267....1
It seems a lot of the dualsport riding I do finds 4th to low and 5th to high. Geared for the same top end, 5th with the 6 speed will be about right.