Gearboxes

Assume you are making a lego car with the sole goal of top speed, acceleration is not a factor. Do we achieve functional gains using a gearbox? I'm trying to make a really fast MoC racecar. I've tried several different gearboxes and many were failures. the few that were functional didnt feel worthwhile. the added weight, complexity, *friction*, motors, etc all seem to outweigh speed gains from the gearbox itself. Direct drive with a single high gear ratio delivers decent performance even if...