If you use 22t at your brake pulley you will experiencing much slower turn at your rear wheel as compare to front. result, it gives you more drag. for the 45T gear diff, the belt seems doesn't fit nicely into the diff and therefore it create drag. I dont have the part number but it should be available in serpent website product section. try to search somewhere JUNE 2006.

Overdrive mean turn faster. If i have front over drive means front turns faster then rear. Standard side pulley is 22/22 overdrive is 21/22.

Only 720 apply 22/21 because the rear diff has 2 teeth higher then 710.

hope thats help