In Winston Cup before that had the quarantine between qualifying and the race guy would run lightweight oil at a reduced level. There was also "qualifying gears". Not special just because of the ratio, but they were seriously lighting.
A lightweight center section will have the housing machined down, gear width at minimum/reduced, outer gear backcut, yoke lightened, AND to top it off the ring gear is BRIDGED. Bridged meaning that between the gear bolt a hollow space is machined out.