Eaton considers their fancy ester Nye 605 a lifetime fluid. Many figured out that lifetime could be longer with some maintenance intervals. I wished that they'd simply tap the engine oil for supercharger lubrication.
Is that the same stuff as the GM supercharger oil ?
$49.95 for 100ml or so at Holden dealer, and you are right, when I got the L67 they hadn't sold a bottle in years...it reeks...Have a GM TSB for M1 5W30 as service replacement. I'd rather change it regularly with say 5W30 than nearly never with the foul smelling stuff...
Yes, the 70w75 is ATF thin but with a GL4 additive package.
If their 75w85 is a similar tech, maybe you can mix 'em for whatever xfer case visc you want. 50:50 could give you 9-10cst.
I've use offroad construction, over the road tractor trailer, farming, and marine,... lubes for years. Plenty of good GL4, GL5, and hydraulic fluids to pick from, and not loaded or dosed with limited slip additives like automotive gear oils.