Transmission keeps upshifting to soon

[bc21]

I have been dealing with an issue with my 2000 ssei transmission. When driving at approx 35 mph my transmission keeps up shifting into over drive. I have tried to track the patterns of what causes it and what makes it stop.
So when I am driving on a flat surface and just holding the gas pedal steady [no acceleration/deceleration] just holding steady all of a sudden the tranny just up shifts in to 3rd then 4th gear. The best way I can explain how the car feels is just like driving a stick and you upshifted into a higher gear to soon, there is no power under the pedal. Now if I push on the pedal really hard the car will then down shift back to 2nd gear and the car will take off. The other quick solution is as i am holding the pedal steady and the upshifting in to overdrive starts to occur, if i let off the pedal real fast and push it again, it is right back where it should be and i have the power back.

It have gotten so tired of it i just use the shifter like it was a manual.

To sum it up it keeps up shifting into overdrive to soon all the time.

Any suggestions would be helpful.

[Archon]

What happens if you leave the shifter in 3rd while driving around town?

[LeSabre in Buffalo]

Is it just unlocking the torque converter? These transmissions love to lock the TCC on flat ground to have better fuel economy.

[bc21]

Thanks for your help

Archon
If I drive it around in 3rd it will be fine at 35 but if i am going around 20mpg it will still tend to upshift and thats when the loss of power begins. Just to make sure Archon I will put it in 3rd and drive it around and report back. I have the interior torn apart because of a water leaking issue in the back seat so it may take a day or 2 to get everything back it.

LeSabre in Buffalo
I am pretty sure the torque converter is locking up (from what i have read about them and how they work). Is there a fix for this.
It only happens on flat ground at a steady pace. The good news here in Pittsburgh there's nothing but hills and mountains, but it is still driving me crazy.


I have 2 ssei so i can swap parts if need be to trouble shoot.

Thanks

[LeSabre in Buffalo]

The TCC is designed to lock at speeds above 28 mph and when in 3rd or 4th gears for increased fuel economy and reduced wear on the transmission. It will unlock without shifting when more power is necessary. The unlock/lock process can feel like a shift.

At least on my car the TCC lock happens at 28 mph. My engine RPM's will drop about 200 RPM from 1300-1400 to 1100-1200 RPM when that TCC lock occurs. It unlocks when speed and throttle position tell it to unlock.

We need some more information on what's happening and engine RPM's at various speeds.

[Wellintr]

My first car ever did this it was a Buick Regal. It was very annoying, a fluid change helped my situation but eventually it happened again and then I got into an accident thus ending my problem never was an issue mechanically just annoying. Sorry no advice just my story and how I ignored it.

[Jrs3800]

bc21 have you checked the functionality of the TPS?

[JEzze]

I no this is a month old anything else on your problem yet. I have the same thing.
I thought it was tps as well as any, no code thought? Im curious how you fixed this.

[redzmonte]

I have not from day 1 liked the way the bonnie shifts. I have been changing the shift pressure, times and mph's in DHP. i have gotting it much better then stock. the stock was way to slow and low, it felt like it was searching for the gear the entire time i was driving. there are a couple spots i need to finish smothing out (low speeds from 1st to 2nd) it is not as clean as i would like but MUCH better then stock. I would go nuts driving it how the factory set it up. I can email you guys what i have if you have DHP powrtuner

S