Star Classic massive mechanical/electrical problem. Please help

[jesseldossey]

I have a star classic 48-4+2 golf cart. Curtis 1268 controller, 48v ADC motor. In the beginning it wouldn’t go past 1.3 miles and hour and violently shakes in the rear end. Gave it to a mechanic and all he did was put water in the bats. Got it back, drove fine for 30 seconds then completely lost wheel power. Pulled off to the side and turned off and on. Then it ran great for about a mile until it went back to its shuddering slow creeping forward speed. I changed the speed sensor and magnet, solenoid, cleaning battery terminals and connects thoroughly, speed controller is getting adequate voltage and not throwing codes. Each battery is good, pack voltage with and without load is correct. I jacked it up the shuddering noise is coming from the differential/motor area. With the cart off, spinning the wheel feels like it’s catching something and has a grinding sound. Also with the pedal all the way down, on top of the creeping slow speed, the wheel has almost no resistance, I can even hold it in place and stop it from spinning. When I hold it in place it also feels like it’s catching something like a gear, every inch or two of spinning. Also today the charger had lights come on and after calling the manufacturer they say it’s battery issues. Gonna leave it on the charger overnight. Could all this be battery problems? Is the differential thing normal? Please help cause it’s driving me nuts. Thanks