Yes there are times you don't want to use motor oil in ATF applications ,back in the early 90s ford mustangs came with ATF in the stick shift trans!!! everybody would make the mistake of putting gear oil in them and they would not shift right but the ATF would not protect the gears and bearings...the fix was 30 wt motor oil with modified gear stops (synchros) and those transmission would last way longer than straight ATF which was used for less drag and better mileage...I think if a puch trans relied on hydraulic pressure like a automatic car trans does, things would be different, motor oil would not work to good. On my tomos I put some slick 50 trans goo in there and it helped that thing alot ...The clutches are going to shred it just a matter of prolonging it...Need better friction material than cork!!! Ha Ha... Kevlar ??? $$$$.......Philo