The best replacement for worm gear is helical gear.

The best alternatives to worm gear are rated as following:
★★★★★  helical gear
★★★★★  spur gear
★★★★  bevel gear
★★★★  planetary gear
★★★  planetary
★★  rack and pinion
★  planetary winch
  hypoid
  helical
  hypoid gear

Your alternative for worm gear is not listed? Suggest!
Speaking about worm gear, one probably shouldn't forget about dc motor.

Other search terms related to worm gear and their ratings are:
★★★★★ dc motor
★★★★ gear ratio
You have in mind a companion for worm gear and it is not yet here? Propose!



Google Trends

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worm gear
helical gear
spur gear