The single bearing was a common way to support the armature in some golf carts. Fortunately, a new motor can be had (if the old one isn't repairable for a reasonable price) for about $350 - $400. There are various on-line sources - some quite a bit higher than others.
If you look up EZ-go, you should be able to find a few. Before ordering, make sure you take measurements of the motor shaft (diameter, spline count, length) and tell the store it is for a Spicer/Dana rear end. Will save some headache in shipping it back if some measurement is not correct.
There are two reasons I can think of that may be an issue - overspeeding and a loose field shoe.
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