Ok, What have I done now... (904 problem?)

Lonewolf3165 said
My brother has a saying, "If you hear hoofbeats, think horses not zebras." In other words, don't over-think the problem. If it was fine before you changed the filter & fluid but not so immediately after, start there. This is a good time for k.i.s.s. Too often people panic & start to reinvent the wheel when it comes to certain things on a car. Transmissions are complex, but most of the time the problems surrounding them aren't.

With regards to the ATF types vs trans failure; I'm an ASE Master Technicain for over 25 years & a shop owner for the last 5. In addition to my own experience I have many friends who specialize in transmissions & have talked to reps. & engineers from major oil companies(E/M) & they all say the same thing. The type of ATF you use WILL NOT cause trans failure by itself. It may change shift firmness somewhat, but minimally. Most customers wont notice. If it fails after a change there is some other underlying pre-exsisting condition that would have cause failure or problems soon anyway. Worn parts, bad seals etc.

No, it won't cause it to fail, but the friction modifiers are much different and cause firmness of shifting as you say, and also slippage. This is an old tranny made to run on the thickest Dex 1 ever made. Now you have a fluid designed to work less with bands than with valving and is a much slicker fluid. There was no problem before, now there is. It is a simple thing to change the fluid and put the proper fluid in. If I am the owner of this car, I drain all the fluid, put the gasket in the right spot, drop in five quarts of Dex II, run it hot and check and add until full.