JC,
'73 TM400 '73 TS400 '77 TS400
1st 30 - 16 32 -15 32 - 15
2nd 27 - 19 27 - 19 27 - 19
3rd 25 - 19 25 - 22 25 - 22
4th 25 - 22 23 -24 23 - 24
5th 21 -24 21 - 25 21 - 26
the primary drive at 68/19 is the same for all so it's only 2nd gear that's the same. cheers