motor D1162 & rear gear combo want advise

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New to the forum and would like some advise. I have a 2001 EZGO TXT. Upgraded to 48 volts (8 six volt batteries) Altrax 500 amp controller, MZJ400 amp contactor, 2 gauge wires, 12:1 stock rear gears, 23" tires and has a D&D motor P/N 170-505-0001. GPS speed is 28 MPH. The D&D motor RPM's like my small block chevy but is probably on its way out based on the grinding noise it is making. Received the GE D1162 motor for Xmas. Was advised that this motor makes tons of torque and works well with the Altrax controller and 48 volts. I live in Fla where it is flat. I want to install high speed gears either 6:1 or 8:1. Has any one tried one of these gear / motor combinations? Don't mind trading some torque for speed but I have no experience with these combinations. Understand that the torque motor spins slower and would require a gear change in order to pick the speed back up. Would like to improve on the 28 MPH. Any advise would be greatly appreciated.