Last year I rebuilt my 4R70W and used Dexron VI instead of Mercon V trans fluid. I didn't realize at the time that the specs were so much different between Mercon V and Dexron VI. I was always used to putting Dexron/Mercon fluid in my old trans. So I decided when I rebuild my trans this time I was going to convert to a better trans fluid than the old Dexron/Mercon. After doing a little research, I really feel like an idiot for not realizing that Dexron and Mercon are so much different now. I was curious if I will have any problems continuing to run the Dexron VI or should I switch to Mercon V as soon as possible? The trans has been working great since the rebuild and I haven't experienced any problems so far.