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Slow acceleration or no acceleration

T

tierzu

New member
2004 Grand Prix GT1
204,000 Miles

If the selector is set to 1 the car will accelerate slowly, and will reach 20 MPH at about 2500 RPM. If you press the gas too hard through 1st gear it will shudder a bit. If you then move the selector to 2 it will shift into 2nd gear and accelerate normally through 2nd. The sames goes from 2-3 and 3-4/D. If you leave the selector at 2, 3, or D and attempt to accelerate from a stop the car goes nowhere. It is my understanding that the selector is simply used to limit the car to a certain gear range, so 1 is 1st only, 2 is 1st and 2nd gear, and 3 is 1st, 2nd, and 3rd gear. The fact that it will only accelerate from a stop when limited to 1st gear seems odd to me. If it were stuck in limp mode it should still accelerate with D selected. It gives no indication that it's in limp mode, and when I hooked my code scanner up to it there were no codes pending or otherwise. I checked the transmission fluid and it seems to be a bit old, but is up to the max mark on the dipstick. I've heard that these transmissions have issues with the pressure control solenoid failing, and it wouldn't be the first time a part has failed or been failing without setting the check engine light. Any help would be appreciated.
 


Would a failed forward band affect only the 1st gear and none of the others? Also would it only affect 1st gear when the selector is on 2, 3, or D? I'll have to test the car again once it cools down before I can determine if the temperature of the transmission fluid is a factor. The other curious thing was that there were no warnings of any kind. I parked the car after driving around earlier today, and then once I started it again and went to drive the transmission began acting up.
 


tierzu said:
Would a failed forward band affect only the 1st gear and none of the others? Also would it only affect 1st gear when the selector is on 2, 3, or D? I'll have to test the car again once it cools down before I can determine if the temperature of the transmission fluid is a factor. The other curious thing was that there were no warnings of any kind. I parked the car after driving around earlier today, and then once I started it again and went to drive the transmission began acting up.
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These trans will do that, my sisters gp had ~75k miles on it when hers went out all of the sudden at a stop light.
 
tierzu said:
I parked the car after driving around earlier today, and then once I started it again and went to drive the transmission began acting up.
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I think this is the biggest indicator of a broken band. One minute everything is fine. Next time you drop it into D... Nuthin'
 
Interesting how illogical cars can be. Just for the sake of my curiosity because I don't know anything about the internals of these transmissions, how does the application of 1st gear differ between the different positions of the shift selector? If the car has to begin in 1st gear before shifting into any of the other gears why would there be no forward momentum with the shift selector in any position but 1? I'm not questioning anyone's deductions or experience, I sincerely want to know.
 
theres more than one band, the forward one busted. its deep inside the tranny, at your miles its rebuild time. it had a damn good run really.

mine made it to 216,000, then just lost 3 rd gear out of the blue.
 


tierzu said:
how does the application of 1st gear differ between the different positions of the shift selector? If the car has to begin in 1st gear before shifting into any of the other gears why would there be no forward momentum with the shift selector in any position but 1?
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Has to do with the manual selection of 1st gear. Actually moves a valve inside the channel plate. This forces certain things to happen, vs. letting the PCM control things with solenoids.

.........and a little magic.
 
tierzu said:
Interesting how illogical cars can be. Just for the sake of my curiosity because I don't know anything about the internals of these transmissions, how does the application of 1st gear differ between the different positions of the shift selector? If the car has to begin in 1st gear before shifting into any of the other gears why would there be no forward momentum with the shift selector in any position but 1? I'm not questioning anyone's deductions or experience, I sincerely want to know.
Click to expand...


He makes a really good point though. Why would he be able to get the car to move when selected to 1st, but not selected to another gear? The explanation of the forward band breaking would make sense I guess (I haven't been into one of these transmissions or Automatics in general,but I do understand how they work to a point), but what difference would it make where the selector is set, it's not like Ford where you put it in 2nd and it starts out in 2nd. The transmission shifts down into 1st when you come to a stop, so what difference technically does having the selector in 1 or D?

Obviously he is in need of a rebuild, but why would selecting 1st even make a difference/

Jeff
 


As far as why does the car move in 1 selector there is a manual band band just like the forward band that will engage when you drop the selector down.

Heres a fun video to try to follow along. At 10:30 he pulls the manual band. Then the forward band.


https://youtu.be/_yDmkz42itM
 
I'll have to check it out later, when I am at a computer fast enough to play a video... I thought I had a handle on it, but then the handle broke kinda like that apply band and I couldn't work it out what difference it made.

Hell I thought my gear selector was just for show, it will up-shift at 4K if I don't have my foot buried in the floor.

Jeff
 
Yes the 4t65e has really interested me and I went and got the service manual after mine blew up. I really like the idea that you can tear down 90% of it while its still in the car.
 
Very interesting. It could be considered a fail safe of sorts to help you get home. I shopped around various shops in the area and found one that will order a used transmission that's been professionally inspected and had the fluid and filter replaced with a 6 month/6000 mile warranty. The transmission has 150k miles on it, and they're charging $580 for the transmission and $650 to install it. I figure I'll end up selling it before the replacement transmission fails. There's a 2006 Grand Prix GXP with 88k miles for $7800 at a nearby dealership I'm trying to save for.
 
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