Harsh shifts in 2004 Impala 3.4L

Joined
Mar 26, 2009
Messages
2
Location
Elgin, IL
I have a 2004 Impala 3.4L with 53k on it. It has been shift harshly recently. When the trans is cold it shifts butter smooth, but after about 15-20 miles of driving every shift is very hard. If I let the car cool for a few hours it shifts great again. That is for first 15-20 miles. Any thoughts?
 
Joined
Mar 31, 2009
Messages
379
Location
Mi
Does the service engine soon light come on?Get it scanned for codes and one known code,1811 will probally come up
 
Joined
Dec 26, 2007
Messages
2,145
Location
NC
Have you ever changed the transmission fluid or had it done recently?
 

cq2120

Thread starter
Joined
Mar 26, 2009
Messages
2
Location
Elgin, IL
The service light does not come on. And the DTC scan performed by Autozone did not show any codes. Is is possible that an aftermarket scanner won't be able to read the tranny DTC codes. And yes the fluid has been changed, and none off the symptoms changed afterwords.
 
Joined
Dec 23, 2006
Messages
163
Location
Maryland
I had a 2002 Impala with the same problem, which acually became worse after a full transmission flush. In addition, there was a whirring sound coming from the left side of the vehicle in the vicinity of the transaxle. After doing some research I learned that it appears that this problem may be caused by a defective pressure control solenoid and GM has issued a TSB (#00-07-30-002B) for that issue. In my case, the harsh shifting from 1st to 2nd gear set codes that the transmission shop could read via a scanner. The GM 4T65 transaxle has a known problem with the planetary gearset wearing out early when driven under certain conditions. If you have not had a pan drop and filter change done I would recommend that service and use the latest version of Dexron, which is Dexron VI. You are at the point where fluid replacement should occur using the severe schedule. I strongly recommend that you avoid a full flush. I believe the flush I had done distributed dirt and metal particles throughout the transaxle exacerbating the issues I was having. I wish you the best of luck and that you can get some more life of your 4T65. We had our unit replaced at 84K miles due to the possibility of an internal failure.
 
Joined
Mar 31, 2009
Messages
379
Location
Mi
Sonnex does sell an updated pressure control solenoid.AutoZone uses a code reader which only read codes.Any aftermarket including the Snap On Modis can read the transmission codes.
 
Joined
Jun 19, 2009
Messages
52
Location
Nevada,US
I have the same problem with my 2003 Impala w/ 3.8 liter @105000 mi. It started soon after I had a complete transmission flush. The shifting for me is a pre-mature hard shift when first accelerating. It seems to clear if I manually shift through 1rst, 2nd & 3rd gears & then Drive. I'll take it to the shop if it gets worse.
 
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