what size rear tires and what rear gear?
heres spcs for drive and driven gears
drive gear is a 15 usually steel and it presses on the output shaft , you need to pull the rear tail housing to install
driven goes in from the side and needs to be installed in the proper housing
for a 400 with 3.42
drive... driven.... tire
15...........39 ........26"
15............38 ........27"
15............37 ........28"