Are the splines the same on that 89, as on my 1985? I think not. Can you guys confirm, please?
If you're referring to the rear driveshaft splines and the pinion gear splines that engage with them, according to Max BMW's parts fiche the change to Z-20 twenty-tooth splines occurred in 2/88. Before then, 16-tooth splines were used on those components. There is always the question of whether a moto has its
original rear drive and driveshaft or earlier/later replacements. The transmission output shaft splines and universal joint splines of all classic Brick years are 16-tooth.