You may be correct for hypoid gearing. In fact Redline does say: MTL, MT-85 & MT-90 are not for use in differentials with hypoid gears.
Didn't mean to mislead anyone except as a last resort for reducing gearbox noise because of the cushioning effect between gear teeth. Forgot about the hypoid gears in the Alfetta/GTV6/Milano transaxles.
In my case, the crown and pinion gears of the 164 differential, in which I am using some of it (mixed ~50/50) is not hypoid gearing, but in effect is just gearbox low angle helical gear design. Should be OK for a long time, plus as I mentioned, am using ~50% or less that and ~50% or more regular Amsoil gearbox lube.
I did email Redline about this specific use before I bought it, and they thought it would be fine, IIRC, if you believe them.
89 Milano (wife's daily driver since 1989, Shankle Sport)
91 164S (my daily driver since 1994)
94 164LS (~Q) (trip Alfa since 2000)
72 Morgan 27 (water time since 1976)
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6
Last edited by Del; 03-18-2017 at 05:43 PM.