Is my problem the transmission, sensor/computer, or something else?

[Compudork]

Vehicle: 2004 Pontiac Grand Prix GT2
Miles: 141,000
Service: Regular maintenance, full tune up at 80K (w trans flush), trans drain/filter replaced (not full flush) at 130,000
EDIT: No check engine light, no other problems.

I have two very intermittent problems:

1. From a full stop, slams into gear. Once in a while at a stop light, when I press the gas, the car hesitates for a moment and then slams into gear. The entire car jolts very hard. This happens maybe a couple times a week at worst (or not at all for weeks). When it first started it would happen like once every 3 months or so. This jolt does not happen in any other gear, only when starting from a full stop - car will usually shift smoothly otherwise.

2. On occasion after smooth shifts while driving around town, the car will suddenly start shifting roughly. It is like a jerky/bump sort of feel at every gear shift. When this occurs it will do it at every gear, and it will continue until the car is turned off. I noticed that if I stop and put the car in park, then go again - the problem will persist. However, if I turn the car off, even for 5 seconds, then restart and drive, it will shift smoothly again.

There seems to be no trend as far as is the car being cold or hot, etc. Both problems seem completely random. The fact that it is so intermittent, and turning off the car seems to stop the problem for a while makes me wonder if it isn't some kind of computer timing issue or something.

I've hear horror stories about some of our local trans shops saying a rebuild/replacement is the only solution when a $300 fix could solve the problem - so was just hoping for any input before I take it in. Thanks for any advice you can offer!

 

[boomerang]

If that was my car, I'd take it to the dealer. An intermittent problem like what you describe sounds as though it could be computer related with the root cause being bad connections somewhere. I'd hate to see you have the trans replaced or rebuilt when what you had was essentially an electronic problem.

#1 sounds to me like the transmission is not downshifting as you slow. But that's a guess.

#2 sounds as though it could be a problem with the torque converter lock-up although typically the car would stall at lights.

You may need to leave the car at the dealer so they can drive it with a scan tool connected when the problem occurs.

No check engine light?

Edit: How long has this been going on? Did it start happening after the drain and refill? You've checked the fluid level - right?

 

[Compudork]

Thanks for the reply - there is no check engine light and no other detectable problems.

 

[boomerang]

I did an edit above.

 

[bruceb]

GM trannys never set a Check Engine Light (at least not on OBD II cars like the OP has) .. The codes and commands the computer is sending to the trans, like upshift, downshift, tcc lockup, line pressures, can all be seen with a good scan tool that has the transmission code read capability. Like the Snap On tool or a GM Tech II can do it.

 

[boomerang]

Originally posted by: bruceb
GM trannys never set a Check Engine Light (at least not on OBD II cars like the OP has) .. The codes and commands the computer is sending to the trans, like upshift, downshift, tcc lockup, line pressures, can all be seen with a good scan tool that has the transmission code read capability. Like the Snap On tool or a GM Tech II can do it.

Good information. I used to wrench on cars every free moment I had. I rarely do anymore. My knowledge is kind of frozen in time.

bruceb knows of what he speaks.

 

[Compudork]

Boomerang: The first problem existed well before the fluid change. But it happened so rarely, it was more a random fluke then a problem (over the course of six months, it maybe happened like 3-4 times). The second problem occurred just before the fluid change, which prompted me to check the fluid level which was low - at the time, I assumed this the problem. Right now, levels are good after the fluid change.

Bruceb: Would most shops have a scan tool like that, or do I need to hit up the dealer or trans shop?? All I know is the local dealer here will charge me $80 just to pull the car in their garage.

 

[Gillbot]

Originally posted by: bruceb
GM trannys never set a Check Engine Light (at least not on OBD II cars like the OP has) .. The codes and commands the computer is sending to the trans, like upshift, downshift, tcc lockup, line pressures, can all be seen with a good scan tool that has the transmission code read capability. Like the Snap On tool or a GM Tech II can do it.

Yes they can set a CEL, through it is highly dependant on the model. On my Camaro (see sig), there are many transmission functions that will trigger the CEL such as excessive slip and etc.

One thing you need to be aware of though is there are many engine sensors (such as MAP) that can cause erratic transmission functions, once again it is highly dependant on the model.

 

[bruceb]

You may be correct. But so far, I have never seen a trans code set the light. The trans may cause the motor to set a check light, like for a misfire or idle speed issue. But so far, never seen my cel for any tranny issues.

 

[TonyH]

Have the system scanned regardless of whether there's a light on or not.

What you're describing makes me suspicious that you have set a P1811 code. Code description is "Maximum Adapt Long Shift". This occurs when the amount of time during any certain gear change goes beyond the allowed limit and that maximum number of attempts by the PCM have failed to bring the shift back within spec.

If this code was set you will have to determine which shift is setting the code. If the duration is over spec on several shifts you may have a faulty EPC (Electronic Pressure Control) solenoid or worn Pressure Control Boost Valve. In the event that it is one particular gear change causing the problem then the problem is with an internal component and will require internal repairs.

My experience has shown me that the clutch packs in the 4T65E are stacked at nearly the maximum allowed clearance using factory parts, giving little or no allowance for wear. Since GM does not offer any selective plates for the clutch assemblies you will have to use a few aftermarket products and some creative engineering to "adjust" the clearances closer to minimum tolerances.

 

[boomerang]

Originally posted by: TonyH
Have the system scanned regardless of whether there's a light on or not.

What you're describing makes me suspicious that you have set a P1811 code. Code description is "Maximum Adapt Long Shift". This occurs when the amount of time during any certain gear change goes beyond the allowed limit and that maximum number of attempts by the PCM have failed to bring the shift back within spec.

If this code was set you will have to determine which shift is setting the code. If the duration is over spec on several shifts you may have a faulty EPC (Electronic Pressure Control) solenoid or worn Pressure Control Boost Valve. In the event that it is one particular gear change causing the problem then the problem is with an internal component and will require internal repairs.

My experience has shown me that the clutch packs in the 4T65E are stacked at nearly the maximum allowed clearance using factory parts, giving little or no allowance for wear. Since GM does not offer any selective plates for the clutch assemblies you will have to use a few aftermarket products and some creative engineering to "adjust" the clearances closer to minimum tolerances.

Where have you been hiding? You sound like a man who really knows what he's talking about. :thumbsup:

I'll speak for the OP and ask, where do you think he should take it?

 

[TonyH]

Originally posted by: boomerang
Where have you been hiding? You sound like a man who really knows what he's talking about. :thumbsup:

I'll speak for the OP and ask, where do you think he should take it?

I've been hiding in a transmission shop for the better part of 28 years.

He should take it to a reputable transmission shop where they can drive the car with a scanner and monitor the shift timing to determine where the problem lies. Since he's little too far from where I'm at he'll have to find one in his area.

 

[bruceb]

Agree. Most transmission shops and most auto repair shops scan tools can read the transmission parameters and trouble codes.
But a dealer or tranny shop would be more likely to properly interpret what is wrong based on those codes since they work with the tranny all the time. Most regular auto shops, do not do their own internal trans work. They send it to a specialist.

 

[Compudork]

Awesome! Thanks everyone for your help (and for your specific expertise Tony!). I'll be taking it down to the transmission shop and let them have at it... while in the meantime crossing my fingers that the fix won't be too extreme.

One last question for Tony: Since the problem is intermittent - is there any possibility they would be able to pick something up in the scan (maybe a saved code?) even if the hard shifts don't occur on their watch?

 

[amdhunter]

Torque Converter? Do you have enough transmission fluid in the car?

 

[TonyH]

Originally posted by: Compudork
Awesome! Thanks everyone for your help (and for your specific expertise Tony!). I'll be taking it down to the transmission shop and let them have at it... while in the meantime crossing my fingers that the fix won't be too extreme.

One last question for Tony: Since the problem is intermittent - is there any possibility they would be able to pick something up in the scan (maybe a saved code?) even if the hard shifts don't occur on their watch?

If codes have been set they will be saved in history. With a P1811 code harsh shifting will occur after the PCM has attempted to adjust the shift timing unsuccessfully 3 times during an ignition cycle. You should be able to return to normal shift quality by turning the ignition off and restarting the vehicle. It will then go back through the automatic adjustment procedure until failure is achieved again.

 

[gw186]

This is the exact issues I have with my 2000 Taurus. Mine lets me know when the shifting has gone to crap by throwing a Transaxle light which gives a code of P0741.

The tranny shop wants $800 to replace the torque converter. I need to do something, I think it may be getting worse. And I think its burning more gas. But of course I don't have the money right now.

When we test drove it his scanner would detect the converter trying to lock up. I think it tries 5 times before giving up. He mentioned it probably is the converter but could be something else. Could be a stuck solenoid or sometimes some O ring on the pump shaft may come off blocking the flow of fluid.

I wish i knew what to do. A little research has led me to believe dropping the transmission is to much work for me. But the solenoid i could do.

Edit - That first shop said $500 to just remove the transmission so I decided to call someone else. They said removal would be $740:Q

 

[TonyH]

Originally posted by: gw186
This is the exact issues I have with my 2000 Taurus. Mine lets me know when the shifting has gone to crap by throwing a Transaxle light which gives a code of P0741.

The tranny shop wants $800 to replace the torque converter. I need to do something, I think it may be getting worse. And I think its burning more gas. But of course I don't have the money right now.

When we test drove it his scanner would detect the converter trying to lock up. I think it tries 5 times before giving up. He mentioned it probably is the converter but could be something else. Could be a stuck solenoid or sometimes some O ring on the pump shaft may come off blocking the flow of fluid.

I wish i knew what to do. A little research has led me to believe dropping the transmission is to much work for me. But the solenoid i could do.

Edit - That first shop said $500 to just remove the transmission so I decided to call someone else. They said removal would be $740:Q

Your problem is a bit different. In most cases with the AX4S/AX4N transmissions the P0741 is set due to failure of a pump shaft support bearing in the valve body. If caught early enough the transmission can be pulled replacing the converter, pump shaft and reconditioning the valve body with an updated design bearing. Wait too long and the pump will fail turning the valve body into a large piece of scrap aluminum and a transmission rebuild to boot.

 

[ddanski1]

I have a 2001 Potiac Grand Prix. Was driving in parking lot. Car acted as though it went into neutral. Does not change when moving the gear shifter. Automatic Transmision. Any thoughts?

 

[hedleylo]

I know it's been years since this thread was posted, but I'm having the EXACT same issues with my 2004 Impala. What was the resolution after taking it to the repair shop? Was it transmission, sensor/computer, or something else?

 

[Justin33]

Vehicle: 2004 Pontiac Grand Prix GT2
Miles: 141,000
Service: Regular maintenance, full tune up at 80K (w trans flush), trans drain/filter replaced (not full flush) at 130,000
EDIT: No check engine light, no other problems.

I have two very intermittent problems:

1. From a full stop, slams into gear. Once in a while at a stop light, when I press the gas, the car hesitates for a moment and then slams into gear. The entire car jolts very hard. This happens maybe a couple times a week at worst (or not at all for weeks). When it first started it would happen like once every 3 months or so. This jolt does not happen in any other gear, only when starting from a full stop - car will usually shift smoothly otherwise.

2. On occasion after smooth shifts while driving around town, the car will suddenly start shifting roughly. It is like a jerky/bump sort of feel at every gear shift. When this occurs it will do it at every gear, and it will continue until the car is turned off. I noticed that if I stop and put the car in park, then go again - the problem will persist. However, if I turn the car off, even for 5 seconds, then restart and drive, it will shift smoothly again.

There seems to be no trend as far as is the car being cold or hot, etc. Both problems seem completely random. The fact that it is so intermittent, and turning off the car seems to stop the problem for a while makes me wonder if it isn't some kind of computer timing issue or something.

I've hear horror stories about some of our local trans shops saying a rebuild/replacement is the only solution when a $300 fix could solve the problem - so was just hoping for any input before I take it in. Thanks for any advice you can offer!

Have you checked your motor mounts and torque strut there is a shift solenoid that the main wiring harness plug into the side of the transmission that's your second and third shift solenoid and you have several shift solenoid inside the transmission do you have a modulator valve control transmission if it is all electronic what type fluid are you using most of them only require dex/merc 5 I've had the same problems using different type of transmission fluid

 

[Justin33]

GM trannys never set a Check Engine Light (at least not on OBD II cars like the OP has) .. The codes and commands the computer is sending to the trans, like upshift, downshift, tcc lockup, line pressures, can all be seen with a good scan tool that has the transmission code read capability. Like the Snap On tool or a GM Tech II can do it.

 

[Justin33]

I've got a 2003 Pontiac Grand Prix that is triggering a code on my transmission my 2nd and 3rd Shift Solenoid my computer is reading it I change the fluid filter and everything in the car runs fine for a week what is your advice on an issue like that



justin33... Do NOT post in threads this old... If you have a question then ask it...

AT Moderator
Bartman39

 

[pauldun170]

Great posts by TonyH
Learned something new today.