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Lots of cars and trucks used overdrive in the 50's and 60's. Ford even had a two speed rear end that they used in the thirties and fourties.
Overdrive allowed use of a higher geared rear end so low powered cars could have some snap, then overdrive allowed decent highway mileage. Some brands such as Studebaker and Nash got very acceptable gas mileage using overdrive and promoted it heavily.
Use dropped because manual transmission sales, even in trucks, dropped to a fraction of what they were. Big commerical trucks continued to use two and three speed rear ends to accomplish the same thing.
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