Ah this video from BigX event. Those people are all well known D1 drivers, off course they are good. Not only Silvias, take a closer look you can see Skyline R32, Skyline R34, Soarer, 180SX...
Helping a fellow trekker with problematic awd transfer box.
It's the small gearbox that mounts onto the main auto gearbox, with 1 output to right driveshaft, and another 1 output to rear longshaft.