Jeff, What is your target speed range? Speed takes power no matter if you have a transmission or not. A 1-1/2 hp motor can only produce about 1119 watts continuously, and mabe as much as 1.5x more for all practical purposes "continuously" (depending on heat dissipation and size of motor), and 2-3x more peak.
For a permanent magnet motor, torque varies directly with current, and speed varies directly with voltage. Heating losses vary with the square of the current. This means that what you are really trying to do with a transmission is allow the motor to run at a higher voltage and lower current for a given power output to improve efficiency, and reduce heating losses. Heating losses are directly porportional to armature resistance. A larger motor has a lower armature resistance and can handle higher amounts of current while still running efficiently. What follows then, is a way to get a similar benefit to having a transmission is to use a larger motor (or two motors). Also what can be done to get a similar advantage to a transmission is to get a higher voltage motor or over-voltage the existing motor. If the existing motor is over-voltaged it will have higher continuous power capability, and will run at a higher voltage and lower current for all speeds (provided you gear it to where the vehicle would have the same top speed as it would while running at a lower voltage, meaning you'd need to raise the gearing). Regards, Andrew
