You are right to be concerned. I have chewed and broke up so many parts and gears due to rocks. Metal gears just mean a truck that rips to a grinding stop when a stone gets stuck! That just adds up to other broken parts!The 2 speed came with the car and I got an alloy viscous diff, so it has the sleeve already.. This car came with alot of upgrades!!
The only reason I was asking was mainly for the gears, I just don't want there to be little rocks that would get stuck there and crap out the gears.. People that have been running the car for a while tell me it is fine the way it is, but I always like a little extra protection!!
Thanks for the info though