When to change MT fluid/differential?

[skibumdc]

I was reading through the service manual, and I never saw an interval to change out MT fluid, or differential fluid for that matter?

Seriously?

Every 30K, 60K?
Anyone use Royal Purple? Redline MT-90?

Any info on servicing the differentials?
I searched the DIY but onyl saw rear differential write-up and no mention of intervals.

Thanks all.

[Doctor]

I changed mine with
Motul Gear FF Competition 75W-140
Both the tranny and the differential.
1.8T Engine, 5litres in total needed.