I looked for this issues, but could not find anything really close to it. I had just bought a 99 SLE a week ago. Shortly after I got it I had the battery disconnected. When I started driving it after that, the transmission shifts weird right at 3k rpms. It is not a hard shift, or a slip, but weird. It feels as if it is not sure which gear to go into, or if it should stay in the previous gear. It is only right around 3k rpms. If I keep it under that, it shifts great, and over that it shifts great. It almost seems as if it is only when the throttle is in that one position. Up until i disconnected the battery it shifted perfectly. I know the throttle body needs to be cleaned, could it be something to do with the MAF sensor? Because every so often I will start the car and it will just stall after a couple of seconds. And to get it to restart I need to open the throttle a little. I do not know if they ould be related; I honestly do not know much about the 4T65E, I barely knew anything about the old 4T60 in my old 96. If anyone has any suggestions...

BTW, the transmissions fluid looks great, nice and pinkish red, and does not smell burnt. I am hoping it is something simple.

Thank You in advance!

Check for codes. And check the throttle position sensor.

P0440 popped up this morning, but a evap leak would not cause any of this would it?

On a side note my check gages light is on; but all the gages are in normal operating areas...

I'm not sure about in the bonne, but in some cars, when the battery has been disconnected for a while, the pcm is reset, restoring the transmission shift points back to factory settings. It might just take a while before it adjusts to your driving habits again. I might be completely wrong on this, but it was just a thought.

That is what I had thought at first, but wouldn't factory settings be all old people and cushy shifts? I am just thinking what there demographic was for these cars. LOL

Maybe thats the problem..its just that random spot right in the middle of the shift points. I know the Centuries are weird at a certain rpm..they shift in a weird spot to 3rd gear, and its right in the middle of the city driving speeds..when you need to accelerate slowly, the power just isn't there unless you step on it, and o/d cuts in and it drops down a gear. I don't know. haha

A 4T65E has adaptive learning, so your adapts may have been reset. You should just kep driving the car to see if it re-adapts.

This is my first plan of action... since it is the cheapest. After that then I will try some more drastic measures.


Thanks everyone

Well the shifts have gotten better, but they are still not quite right. Sometimes they are buttery smooth, other times they are just not right. It still always shifts perfect under 3k rpms, but over that is hit or miss...

Ok, well now it has been over two months, and it has not gotten better. I have changed the tranny fluid and filter. I also took out the accumulator and sanded the walls, but it is not any better. It shifts perfectly fine at or above 3k RPMS when cold, but once it is warmed up it shifts hard, or shutters going into the next gear. I checked for codes, and there are none, so no P1811. What else could be making the car shift weird above 3k RPMS when warm? Could the TPS or MAF cause that?