If you look at the types listed in post 2 you will notice that they are mild EP GL4 rated. You can use a non EP oil like GL1 for light duty OK but the GL4 rated lubes are mild enough that they can be used in overdrive transmissions that require mild EP. As was mentioned, there is a risk using high EP GL5 lubricants in the old transmissions due to the phosphor bronze bushings in the 2ng gear, reverse idler gear, and the thrust bearing on the cluster gear. The higher EP has a more acidic property in it to attach the phosphorus to the gear teeth for extra pressure but it also munches away at the bushings and synchro blocker rings. The viscosity can be multi type with polymers or straight grade as long as it is appropriate for the temperatures where the vehicle is being operated.
