My transmission specialist (who knows GM 4T65E transmissions inside and out) recommends NOT to flush it. Simply change its ATF fluid and its filter. Let drain via natural gravity - NO flushing. Outward pressure (from presssurized flush) is very bad on these transmissions and its inner gaskets / seals - so I've been told.
Also... These 4T65E transmissions runs "hot" from factory. Yes. They are cool in the winter and on flat roads but up hills or under weight loads, this transmission model heats up fast. Too fast. With this in mind, do install an Aux ATF transmission cooler. Use LPD (Low Pressure Drop) design for attached 5,000 lb. trailer - even if you do NOT tow a trailer. Install LDP like Tru-Cool or Hayden brands. re: 1678 @
http://www.transmissioncoolers.us/Me...ansaver-cooler
If wondering, my mini-van's transmission cooler (covered in winter time) is:
http://i178.photobucket.com/albums/w...interRAD-1.jpg
Hope this helps as well...
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