Red Line oils

The T5 does require Ford Mercon (or equivalent) auto trans fluid. Not sure off the top of my head what weight gear oil the rear takes, it's been a while since I looked at it. Red Line or Royal Purple are good quality oils though, so you should be safe in using them.

I run D4 in the T5. I wanted to use MTL but RL was against it (Hanlon or someone like that doesnt mind seeing folks use MTL though, as I recall. Check it out yourself for confirmation). The D4 seems to do fine, even in 110*F.

For the rear, check out Redline's site. I recall a chart showing that their 85W-140 flowing better when cold than standard 75W-90! Also note that in some later 8.8's, Ford recommended an 85W-140.

When I do the 94's rear, I'm going 50/50, I think (I need to double check that Redline chart). Make sure you get the stuff for LSD's.

Good luck.