On my 1994 Astro I am going to do a pan drop & filter change, should I stay with Dexron 3 or go with Dexron 6? Is it ok to mix the two? I have heard of horror stories about a flush on these transmissions, true or not I would rather just drain the trans. a few times and refill until all is clean. At Walmart the price for 6 is just a little higher than Dex 3. Is SuperTech OK to use? sorry a lot of questions bit I would like your input as I want to keep this van for a long time.