My year and later most definitely use Mercon ATF. At some point in the past, older trucks did used gear oil like 80 or 90 weight. Just make sure where you fall in the range. If you don't have a owner's manual to tell you what it takes, call the dealer and make sure.

Edit: Each manufacturer and tranny design is different. For example, my 1982 Toyota Celica used 80W90 but my 1999 and 2001 Honda CR-Vs use Honda MTF which is basically motor oil with special additives.

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2011 Ranger XLT, 4X4, 4 door Super Cab. 4.0L, 5 Speed M50D-R1HD, 3.73:1, 8.8" open differential, Jason Pace cap
2019 Ford Ranger STX FX4, Super Crew, 2.3L Ecoboost, 10 speed automatic, 3.73:1 with rear locker, Leer 100XR cap