Drag Racing Rear end oil changes

[squares98]

If I make 40-50 passes a year and put 15,000 miles on the car a year how often should I replace rear gear oil?

Also what about trans oil?

 

[Gearbanger 101]

Every 45,000miles/70,000km is fine. A few short duration quarter mile passes aren't going to heat and degrade the oil any more than usual. It's under severe long term running conditions like road racing that the interval changes should be more frequent.