My kubota kx91-3 quit moving

Hi guys
I think I just became a victim of the broken final drive. My KX91-3 just lost any movement on the right drive motor. It makes a whiring sound but won't move? I pulled the oil plugs and there is no sign of any steel flakes in the oil. Any ideas what this might be and also how to remove and inspect the drive? If it is a defective drive, can they be rebuilt?

Thanks again
Scott