What is the best transmission fluid to use in the Hydramatic 303M 4 speed automatic transmission used in a 1956 GMC M-220 Duce and 1/2 6X6. The plat on the truck shows to use OE 10 for below 32 Deg. F operation and OE 30 for above 32 Deg. F operaiton. These are old designations for 10 and 30 WT Non- Detergent motor oil. I have also heard that people are using Dextron III Transmission Fluid. Many of the tractors and some of the automatic transmission trucks are using Trans Hydralic fluid. I looking for the best alternative where I wont have to change oil in the transmission if I use the truck in winter. Please reply or give me a contact that could help me with this.


Kenneth L. Hollingsworth