Those wheel drives are expensive. I would go through the process of filter, fluid and making sure the wheel drive is bled of air first.
I had an issue with one of the drives on my Toro (commercial unit) and they tried telling me the drive couldn't be rebuilt and wanted over 700 bucks to sell me a new one. I had nothing to lose and tore it apart taking pics as I went. Turned out I needed to replace the sealed bearings. I replaced both and for 4 bucks and a little time I was back up and running.
