As you have noted a rack and pinion is not generous with efficiency. Could you at all incorporate a lead screw system instead? Better yet a ball-screw lead screw and efficiency goes up quickly.
Maybe give us a better idea (plus sketch) of what you are trying to achieve and we can give a better idea on what might work to achieve that goal.
If you are going to stick with the rack approach, then some load figures, distances and speeds will be more useful here. It is impossible to asses issues when we may be talking about moving 17-ounces or 300 tons.