That's a Savox 300oz waterproof servo. I used the DAK Painting guide. To get the finish. The trucks I saw on the net had a lot of black bits. I've also added a scale interior and working mirrors and such as mine is an FPV rig.
i bought a Tamiya three speed and I have a transfer case on the way to go with it. The stock transmision has some slippage under heavy loads climbing. I think the Tamiya will be better in that respect and the parts will be more available. I might even upgrade the diffs at some point.