I buddy of mine told me years ago never to do it on a high mileage tranny. I found this while surfing which is basically what he told me.

http://www.trustmymechanic.com/transslip.html

Please understand that I do not have a huge knowledge of trannys. My buddy is 20 years older than I am and knows his stuff. I had an old blazer that the tranny was slipping in so I did the fluid and filter change. When I was done it wouldn't even move. <img src="/forums/images/graemlins/evil.gif" alt="" /> I am by no means being a know it all but am trying to just help out. <img src="/forums/images/graemlins/cheers.gif" alt="" />