Posted by Ken Dunnington on Friday, September 01, 2006 at 1:07PM :
In Reply to: Gear oils for our old irons posted by Mike (Montreal, Quebec) on Thursday, August 31, 2006 at 11:05PM :
Yes, I, just as most folks have, used regular GL-3,4,5 spec 90W(or 80W-90W) in many transmissions and transfercases for years without any known troubles. I never thought twice about it. But I've had multiple NP435s with bad blocking rings/synchros so *perhaps* these were victims of this practice. Thus I have made the change to using non-EP oils in the transmissions and transfercases I run.
As I think I put in my last post of that thread, the OEM of my 1973 IHC states for the T19(transmission) and NP205(transfercase):
"Use straight mineral oil SAE-90 for temperatures 0 degrees F and up. Use SAE-80 for temperatures below 0 Degrees F. SPECIAL RECOMMENDATIONS: Where temperature is consistently below 0 degrees F and where parked vehicles are exposed to unusual cold for long periods, use SAE-75. Where temperatures are consistently above 90 degrees F(unusually hot), use SAE-140 straight minreal oil."
Again, this is quoted from the owner's manual printed in 1972.
Ken