IF you have a jeep like Darren posted above and you are asking can you swap in parts from a 3 speed Super Gaucho the answer is no. They use a different Floor Pan and other parts. Its not as simple as just changing gear boxes. While teh body looks the same there are lots of parts underneath that are different.
Darren said it you can go to 18v reliably or you can go with a 24v scooter controller setup if you want more volts to relieve stress on motors and gearboxes.
ok thanks alot. hard to believe them little motors pull that much could u maybe tell me y it is cutting out when in second gear for any length of time ? and sometime i hear a clicking ? they are new gear boxes and new stock motors and harness too everything new just replaced? did i wire it wrong still on 12v for now to with original harness