i honestly havent a clue what pipe to use i used the blue aluminum pipe from traxxas on mine and seemed to work rather well ,with the TM i would make sure you tear the diffs down and shim them to take most all the play out or you will grenade them
as for tranny gears the only problem i had was when i was using revers and kept blowing the forward and reverse gears and the idler gear ,but with the FOC no problems there they are gone ,
with the stock slider axles ,you will twist them like nothing ,try and find CVD's for it or try this mod to make them last longer
take the axles out and try removing the universals from them and take the female shaft and install it on the diff side and the male end towards the wheel i did that and they seemed to last alot longer with no problems