If you drive very light footed it will change throught the gears very quickly, and you'll be in top gear in no time, doing plenty to the gallon

Floor it in each gear and it will hold off changing till it's upper design rev limit.
Some boxes, like my Ford AOD, you can get valve sets to allow you lift the revs it would normally change at, to whatever suits the power, but only by removing the box sump, not during everyday use.

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