Update from OP: Cart was returned to original dealer. Mechanics there could not find the cause for the whining/grinding noise. The invoice indicated the controller was “computer tested” and an additive was added to the “rear end.” Cart was test driven but they “found no issues.” Verbally, I was told it is safe to drive the cart and if EZGO receives a lot of complaints about noise issues they will investigate and possibly issue a recall. So anyone having the same problem should contact EZGO in addition to complaining to the dealers.