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Impala While undergoing many facelifts in its history, the Impala has proved itself to both civilians and police forces as one of the most capable 4-door cars GM has ever offered. Currently moving towards its 10th generation the Impala is one of the longest lasting and popular models.

2014 Chevrolet Impala
Includes: Bel-air
Platform: B-body & W-body

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Old 04-01-2008, 07:18 PM
Join Date: Apr 2008
Posts: 5
Default transmission shifts hard when hot 04 impala

i have a 04 impala, recently i have been having alot of trouble try to find out why my transmission shifts hard when only its hot should i get a external cooler?
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Old 04-01-2008, 07:29 PM
CF Junior Member
Join Date: Feb 2008
Posts: 65
Default RE: transmission shifts hard when hot 04 impala

No the cooler will not help, you need a pressure control solenoid. When the solenoid gets hot it shorts out internally and commands full line pressure to the trans causing hard shifts.
GM Tech
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Old 06-15-2009, 03:32 AM
CF Beginner
Join Date: Jun 2009
Posts: 7

This is for KTM hey i am having the exact problem. I have two questions 1 is that common in 04 impala's? and 2 would a shorted out pressure control valve also be the cause of a delayed shift as in it sounds and feels like its about to shift and pretty much does but kinda drags into a gear like the car is sayin "im not sure if i need to shift buuuut i will"? sorry didnt know how else to explain it.
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Old 06-15-2009, 06:07 AM
CF Active Member
Join Date: Apr 2009
Posts: 139

RJwood, my guess with you would be to check the fluid level on your transmission. Could be there is not enough or maybe even too much fluid in it.
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Old 06-15-2009, 06:43 AM
HotSauce6226's Avatar
Impala Super Moderator
Join Date: Jan 2008
Location: Shelbyville, KY
Posts: 813

Originally Posted by folmsbee View Post
i have a 04 impala, recently i have been having alot of trouble try to find out why my transmission shifts hard when only its hot should i get a external cooler?
Maintance at all?
plugs wires?

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2003 Chevy Impala - Base 3400 - Few Mods
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Old 06-15-2009, 06:55 AM
CF Active Member
Join Date: Apr 2009
Posts: 139

If your car originaly comes without an external cooler AND you havent put in an other gear box, then why would it all of the sudden need an external cooler?
Shouldnt you be able to get an error code from your gear box on those '04 cars?
I would also go for the solenoid.
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Old 06-15-2009, 09:55 AM
milwaukee_01impala's Avatar
CF Junior Member
Join Date: Oct 2008
Posts: 50

when the fluid heats up, it thins a bit. if the PCS is on its way out the fluid will start seeping past the PCS when its not supposed to. the puter will "see" this and max out the line pressure in the tranny to try to stop that from happening. and since there is fluid going past the PCS when its not supposed to, and the line pressure is maxed,(meaning even more fluid is seeping past the PCS) it will give you the hard shifts since the tranny cant get the right pressure to shift.
the 4t65e transmissions in the w-body cars are known for the PCS to fail. its a fairly common problem in these trannys.(knock on wood) but i have 114,000+ miles on the original tranny on mine, and wehn the tranny gets hot in mine it starts to whine a lil bit. but i dont have the hard shifts.
if it indeed is the PCS thats starting to fail it will usually throw the P1811 code. but this will not cause the CEL to come on. the code should be stored in the pcm.

one more thing, if it indeed is the PCS and you get it repaired, the tranny fluid will have to be changed. this is a good time to drop the pan and change the filter also. and dont get the dexronIII fluid, get the new dexronVI fluid.
2001 impala, 3.4, 1.0dhp pcm, fenderwell intake w/k&n filter, 2.5" downpipe-exhaust w/flowmaster 40, 17" helo slick rims, LED tail lights/front turn signals, multi color led LS cluster/ hvac controls, impala embroidered floormats, 20% tint, aftermarket moonroof, turn signal mirrors

Last edited by milwaukee_01impala; 06-15-2009 at 09:58 AM.
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Old 06-25-2010, 08:59 PM
CF Beginner
Join Date: Jun 2010
Posts: 1
Default impala shifts hard when hot, p1811

I have done some research on this problem and it turns out it is common with GM transaxles 4T60E and 4T65E. It shifts nice until it gets to operating temperature and then BAM. It is suppose to be a defective PCS in the transaxle. I wonder if they go bad because it is operating at higher temps since it is using a portion of the radiator which temps are over 200 degrees. This is a common problem from 97-2005 vehicles. Here is the number of the GM customer service rep I have been dealing with in this matter. I figure she is the best one to contact since she is now knowledgable about this problem (instead of getting a bunch of different reps that hear it for the first time). 1-866-790-5600 ext 11310, have vin# ready for her and be sure to leave a message if no answer. The main number is 1-800-222-1020. I had them tell me to take it to the dealer to get checked, which cost $90, after I told them what the code was. The dealer checked it and said it will be another $510 to tear out the tranny and further diagnose it. What kind of nonsense is that?
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Old 06-25-2010, 08:59 PM

04, 2001, control, hard, heats, hot, impala, pcs, pressure, replacing, shifts, solenoid, transmission, whine, whines

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