68post
very, VERY, limited access member
- Joined
- Feb 20, 2014
- Posts
- 281
- Reaction score
- 97
- Location
- Indianapolis
- First Name
- Tim
- Truck Year
- 1984
- Truck Model
- 84 K30 SRW Silverado, 85 C20 C6P
- Engine Size
- 454, TBD
I didn't see you get this answered so here you go.
Several yrs ago I asked a customer of mine that is a retired Allisons engineer if using Mobil 1 75w-90 gear oil was ok in my SM465, he said that would be excellent and that they nearly stop wearing at all once broken-in and the fluid changed.
He did the durability testing on this transmission back in the day.
I wouldn't use anything lighter than Synromesh oil or heavier than 75-90.
Most do not know that 75-90 weight gear oil is the same viscosity as straight 30 weight motor oil and 80-140 is equal to straight 40 weight.
Several yrs ago I asked a customer of mine that is a retired Allisons engineer if using Mobil 1 75w-90 gear oil was ok in my SM465, he said that would be excellent and that they nearly stop wearing at all once broken-in and the fluid changed.
He did the durability testing on this transmission back in the day.
I wouldn't use anything lighter than Synromesh oil or heavier than 75-90.
Most do not know that 75-90 weight gear oil is the same viscosity as straight 30 weight motor oil and 80-140 is equal to straight 40 weight.
