I looked up on the Auto-RX website, as well as the past posts about using Auto-RX with transmissions, differentials, and power steering systems, and I see nothing stating that synthetics will interfere with the Auto-RX's cleaning capabilities. For engine oils, it appears that synthetics do interfere with Auto-RX (or at least on the rinse phase) but has there been any proof that synthetic ATF or gear lubes will interfere with Auto-RX?