OK going from memory here back in the 70's the Allison V-drive used straight 30 weight motor oil. I don't remember if it was regular or Non-detergent. Yep a very bullet proof tranny. Kinda like a powerglide for transit busses. Had 2 speeds forward, low was to get you moving and then when it got to 20-30 mph (depending on gov. setting) it shifted into direct drive and locked up the torque converter. The only down side of the V-drive was getting them in gear with an ice cold tranny. Lots friction with that cold oil and some gear teeth grinding until they all stopped. Another trick on the 70's vintage units, there was a switch in the shifter that was activated when the lever went into the F or R slot. The clutches didn't engage until the switch was closed. You could release the clutches without taking it outta gear. Kinda fun playing with a rookie driver, just slip the lever out of the slot when he wasn't looking and the bus doesn't go anywhere. Spent a few years going around in circles at the wheel of a transit bus back in the 70's.