Ok, i just want to make sure that you know the difference between tranny slipping and tranny shifting hard. Being said, lets go to tranny slipping. If the tranny is slipping, its slipping. A frequent transmission oil change is only preventative maintenance to prolong the transmission.

Here is what i'm doing this weekend since i felt a little of a harder shift at halfway throttle on 1st to second. I'm going to be buying around 15 quarts of reg tranny fluid that are in the big 5 qt bottle (so i need 3 bottles), and then buying 5 quarts of valvoline maxlife, a tranny filter which comes with the gasket. I am going to drain and the fluid, replace the filter, drive around for 20 minutes and jack up the car again. I'm going to drain the fluid again, refill using the 2nd batch of 5 quarts, drive around for 20 mintues..come back. Drain the fluid, drive around fro 20 minutes, use up the last 5 quarts. Drive around a 10 minute again, drain the fluid, and the refill the tranny with the valvoline maxlife. Reason why i do this with 15 quarts is that if i'm not mistaken, there is about 10 quarts of tranny fluid in the tc? i forgot exactly how much, but this ensures that you have almost all new fluid in your transmission. If you want to make sure that you have almost all new (you'll never have all new unless you drain the tc by removing it or doing the flush) do it more times. is it a pita?? yes...is it necessary? you're the one to decide.

Again, if your tranny is on its way out, there is nothing really you can do. But sorry to yell, AT LEAST DRAIN AND REFILL YOUR FLUID AT LEAST ONCE!!!!!!!!

 

I had the problem LOR1DA is talking about.After 30 minutes of driving I would loose overdrive.Brand new radiator.I again replaced the radiator with a more expensive one and the tranny is fine.So it could happen to just be lack of good transmission cooling from your new radiator.But you should do something about your nasty fluid.

 

Well the radiator i got in now is an all aluminum high quality radiator. There were no warning about not having tranny cooling lines and it says its for automatic. The transmission actually started slipping when I noticed that my first radiator was cracked. The fluid is definatly burnt and brown. It was about a half quart low so I filled it and it still slips. I guess I have to drain and fill. Hope it works.

 

The drain and refill will be a good idea, If the fluid was dark red or dark burgandy but If the tranny is slipping than that will have to be corrected by pulling the tranny apart.

 

first you should smell the fluid if its black and smells like poo poo dont change it if its a little brownish your on the edge feel the fluid if it feels like sand or crap (not that i would know what crp feels like or anything) dont change it if its a little brownish and smells ehh your alright but it should still have a red tint

 

holy horse crap! That is such BS that it's not even funny. Don't believe everything you read in the 4th gen forum. You'll live longer.
A trans fluid and filter(screen) change is never harmful...