OldIHC

The manual calls for 90wt gear oil in cold weather and 140 wt in hot , I remember other possibilities mentioned on this site , or am I imagining that ? I have a gallon of 85/90 with additives by fram and before I put it in ,thought I would ask .

There is one transmission IHC used that called for 10w-40 because of the small needle bearings used on the countershaft> I think that was more in the Loadstar time period.
For ever other trans, I run and recommend SAE 50 engine oil. Same viscosity (or close too it) as 90 GL and handles heat better.
You are going to be hard pressed to any damage with whatever lube you choose, as long it is the one that has all the small needles, I can't remember if it was a Spicer , Warner or other mfg, but do remember is was more toward the 70's.

Thanks Niki and CB , I remember when I was having noise problems you recomended other than gear lube and it did make a difference .