These transmissions use ATF only because they utilize a Wet Clutch system which has multiple disks and plates with fluid as the transfer medium. They wear out but are more hardy than a dry clutch. The oil is dependent on the viscosity remaining the same which degrades with every engagement (shearing) event. Then there are all the other additives...motorcycle guys really get into the nitty gritty with the high RPM rocket ships. New fiber disks and plates are provided in a rebuild kit...hardly OEM. In Marine use, where a boat sits for periods, some claim the disks can dry out and become unbalanced. Plates are typically damaged by heat, which is less likely with the speeds of the gearing our clunker see. Water contamination is always more likely in Marine applications. So changing oil on a yearly schedule is good advice. Examine the removed oil for color changes (heat damage), smell, water settlement, and emulsification (white greasy). On Diesel engines, Mobile even had a field test kit which consisted of a two-lane channels. New oil in one, old oil in the other...tip it up and the flow race was compared. In another a ball bearing was placed in a machined cylinder of oil, and flipped over like an hourglass. The cap had glass ports fitted on the ends and you would time when the ball bearing arrived to calculate viscosity. Finally running equipment is always healthier in the end. Run your engine (or turn it over) regularly.
One last sea story. We had a gangway gearbox trash out on us. We exchanged Port to Starboard and stripped out the damaged gearbox. One of the guys says, Heh!, that looks like the guts of a Toyota Pickup axle...and it did! We were looking at a few months running using come-alongs.. I ended up ordering a new gearbox using a VIN number for a new pickup as a part number. It got way up into purchasing before we got caught, the reason we got caught was the vendor wanted to know what color...but the best part was that our way was cheaper! We didn't get our dock truck.
One last sea story. We had a gangway gearbox trash out on us. We exchanged Port to Starboard and stripped out the damaged gearbox. One of the guys says, Heh!, that looks like the guts of a Toyota Pickup axle...and it did! We were looking at a few months running using come-alongs.. I ended up ordering a new gearbox using a VIN number for a new pickup as a part number. It got way up into purchasing before we got caught, the reason we got caught was the vendor wanted to know what color...but the best part was that our way was cheaper! We didn't get our dock truck.
