Change the brake fluid every three years. Differential fluid every 50,000 miles if it's not synthetic. Tranmission fluid according to the owners manual. Power steering fluid at the same interval as the tranmission. Engine coolant according to the owner's manual (I think every two years). Transfer case fluid according to the owner's manual. The Ford site has electronic versions of all the manuals if you didn't get any or are missing some from the previous owner.

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Sgtsandman's Work in Progress
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