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I notice this has been posted a long time ago so I don't know if you will respond or not...but I'm hoping you can tell me what you ended up doing about the problem. I have a 2000 Grand Prix and having the exact same problems. It has been in and out of the shop for a month now. He has already replaced the sylenoid (or so he said he did), among other things. This week he is planning to replace the valve body, and the problem only seems to be getting worse...I feel like I may be getting screwed here, I've spent enough I could have just bought another transmission at this point...  

nebdrummer:
I also have a 2000 gp se as well and it  has just started doing this.  The car has 127000 miles, not abused, just alot of highway miles.  It starts out fine then after about 20 or so minutes it will start shifting rough as stated.  That and when going from drive to neutral while crusing, it bucks hard like it went down a gear to get to neutral. My car does not reset after just turning it off and back on.  It has to sit for a couple hours for it to shift normal again.  Does this sound like the same sort of symptom,?? This solenoid? This coming from a poor white boy who likes to take care of his stuff.. .. ahh poo!!


Also would like to add.. i dont know if anyones problem is also doing this.. but when it starts shifting hard, it whines. it almost sounds like i have a big old supercharger under the hood. and.. i know that it isnt good.  

I notice this has been posted a long time ago so I don't know if you will respond or not...but I'm hoping you can tell me what you ended up doing about the problem. I have a 2000 Grand Prix and having the exact same problems. It has been in and out of the shop for a month now. He has already replaced the sylenoid (or so he said he did), among other things. This week he is planning to replace the valve body, and the problem only seems to be getting worse...I feel like I may be getting screwed here, I've spent enough I could have just bought another transmission at this point...  

oh...

same info is needed..

copy and paste this link to a P1811 diagnosis..

its 5 pages  long...

http://ww2.justanswer.com/uploads/mcvgreg/2008-07-13_150302_2000-Century-P1811-Chart.pdf  

this same problem has acurd to my 01 grand prix gt it is at ken depoltz getting the pc seliniod replaced for a total cost of $300 they have to drop the sub frame and remove a cover it take a dealership 1 day   and i will tell you take it to the paople that work on Gm  they say there like a rock cuz there always in the drive way  

On later model GM cars {approx 2000 up} the computer systems are designed to make the trans shift firmly when certain trouble codes are detected. The reason they did this was that the harsh shift feel would prompt you to bring the car in for service.So you may all have the same symptom but it can be caused by a whole list of different problems.The reason it goes away when you cycle the ignition is the computer resets and wont over increase the pressure until the problem is detected again. A good scan of the computer system and or a good road test should reveal the culprit.

PS: Pressure solinoids work on voltage.The higher the voltage the lower the pressure.So a open citcuit will give you max line pressure. Pressure solinoids can fail mechanically as well but that creates low line pressure and slippage.  

It is possible that the transmission is needing repaired or overhauled, how many miles are on the transmission itself. you can reach me on my site http://www.sstransmissionrepair.com my name is sean or you can call me at 313-388-9499, or stop by anytime for transmission repair downriver area Michigan  

Ok so i have a 2000 pontiac grand prix gt with 141000 on it. I have replaced so much on the car already. Including axels (both), and the bushing and then today the crankshaft positioning sensor. No this didnt happen for the fisrt couple months that i had the car. But now a wierd belt noise happens like its slowing down and it kicks in every gear. Now note this. It only does this when i drive it for a long period of time, or when i drive harsh. But usually or most of the time it stops if i restart the car. But now lately a couple of times it doesnt unless i let it sit for a while. Please Help I dont want to get rid of this car!!!!!!!!!  

i don't understand... i would like to know what color your transmission fluid is....

when was the last time you serviced the transmission...  dropping the transmission pan as you drain the transmission fluid.. dropping out the transmission filter with care so you get the seal from the neck also.. and not break the neck off ...

stick a new filter in.. a new pan gasket... and some fresh dextron... ATF... i don't recall what those take... 4 or 5 quarts...  measure what you take out..

the filter media is dacron.. it can get clogged  block the flow the transmission pump is able to pick up.. the clutches don't get enough pressure... they slip...     total failure soon after...

i just had a lady call me.. 86 S10 blazer... told me her truck was slowing down going up hills...   i checked the engine... ran fine as i had tuned it up a few months back.. plugged in the scan tool... all the data stream number were within spec...  when i grabbed the transmission dip stick... it was 2 quarts low.... i tossed in a few quarts i had..  told her it needed to have the transmission filter done..  she just could not understand..  that the filter being clogged would cause the transmission problems even with the transmission at the full mark...