Yes it should be 1st, 2nd , third, lockup, and Od. What he describes would be like a late 70' s-80's vintage 518 with 3 speeds and lockup. What year is the truck? 2001?
Od should still occur...however there are electrical mods to disable the selenoid from actuating OD. You can add a relay and change the wiring so when the engine is started OD is off. Then you use the OD switch to turn OD ON.
I think grounding the OD selenoid would work but I would think that would throw a code.
Dan, do you run 3:55 or 4:10 gears? Maybe thats why the builder disabled OD, but I would think the tranny would run hotter. When OD engages the tranny is in a mechanical lockup and the TC and planetary are in a free spin mode. At least thats how I'm reading it. The fluid is not under load so it cools down. Using TC lockup only would be a load even on the thickest TC clutch facing.
Dave, cut and paste is an amazing thing.