I've always used Redline blue in the box and red in the diff, box was changed after 8yrs (because I picked up some cheap) with a few Motorplex days and a bit of cone racing, and the diff oil is well over 11yrs old and going strong - but I have only done about 70,000k's in that time, guess I should change the brake fluid and PS fluid too as it's the same age lol.

I'd recommend Redline any day, just make sure your box is drained for at least a day as it does not mix well with other oil.

__________________
Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.