1999-2002 TRX400EX Fourtrax Service Manual, Page 151Get this manual
CRANKCASETRANSMISSIONCRANKSHAFT Coat the shift fork shaft with oilInstall the shift fork shaft through the shift forks and into the left crankcase
Apply oil to the gearshift spindle oil seal lip
Install the gearshift spindle by aligning the return spring ends with the spring pin bolt while pulling the gearshift plateEngagethe gearshift plate with the shift drumAssemble the crankcase halves (page 11-14)