The right oil for GM tranny is it Dexron 6??

[goldenbird]

purchased an X5 3 days ago with GM steptronic tranny and 113000 miles (2005 model). The failsave program occurred once in a 3 nearby short trips. parking the car for a few minutes solved the problem.error code is found to be p0734 gear monitoring 4 (error during up shift from gear 3 to gear 4). My experienced tech suggested to replace the tranny oil with the one approved by BMW (68$/Liter) as this might be the preventive solution and denounced replacing it with Dexron 3 as it is an outdated oil that might corrupt the tranny instead of protecting it. According to my research it is found that Dexron 6 is the right choice. Is it right? And was it satisfactory for those who replaced their tranny oil with Dexron 6??