A different way of saying what was said above
You basically got two gears here
1) Driven gear ..........
the one everybody replaces which is a snap to take out on the side
of the trans tailshaft
2) Drive gear
this one is installed INSIDE the tailshaft and drives the driven gear
To replace this gear.........
you gotta take the tailshaft off the main part of the trans
410's are too steep to make things right by just changing the driven gear
because none available will work
You gotta change out that drive gear so it then will be a good companion
to work with the driven gears which are available
I'd so the Speedcal thing before going to all that work
Hope all that stuff makes sense
Grady