I can't speak for an 8LL,but an 18 speed is very similiar to a 9 speed direct(not OD) tranny (5 gears on the bottom,4 on top)
You have a range select,and a splitter.The splitter can be thought of like a 2 speed rear end.It can be used in any one of the 9 gears,thus you've 18 speeds total.
It has reverse far left and foward,straight back is 1st,forward and over 2nd,then a regular "H" pattern too 5th.Then range select up,go back into the hole used for 2nd(towards dash,in middle)that's 6th,and again "H" pattern until 9th.
The splitter will move 1/2 gear between any two gears,like the split rear-end analagy.
13 speeds,and 15 speeds,are the same as 18 speeds,except the splitter only works in the top(13),or the botttom(15),not both like the 18 speed.
9 speed OD trannys have 4 gears on the bottom,5 on top,so they shift in a different pattern than the 13,15,or 18.
18 speeds are excellent tranny's,as are 13's and 15's,but with the advantage of the splitter in low and high range.
I hope that helps,more than confuses!!