I have done a bunch of reading on upgrades and parts for the stock 3706. What I decided on is:
RPM Carriers #80372-#80382(Front and Rear)
Steel Idler Gear #3696
Steel Ring diff #2381x
5x11x4 metal bearings
I am still deciding between the XL-5 ESC w/12T Titan motor, or going with the Velineon brushless system #3350
stock has a 18t pinion gear along with a 84t spur gear, when I upgrade to either the 12T titan or the brushless should I change the gears? I read that higher teeth will be higher speeds but I am mainly using this for offroad and not pavement.