Metal shielded bearings are used on all the internal locations, while on the external locations, rubber shielded bearings are used. 1 on the input shaft (motor side), and one on each end of the output shaft.
On final assembly, I dab just a small bead of silicone on the mating halves of the transmission.
How well does it hold up?
On 4S Lipo, it holds up very well.
On 6S Lipo, it surpasses 50mph in a light weight E maxx. The weak link on 6S seems to be the output gears. It will eventually rip the teeth from the output gears from accelerating so hard.
It's pretty hard to control on 6S though. 4S is my preferred setup.