2001 GP GT "No Overdrive"
MoDoggie
11-04-2010, 09:59 AM
I have a 2001 Grand Prix GT with 178,000miles. The overdrive quit working. Will this require a full tranny rebuild or can this problem be fixed by itself? Also, is it still ok to drive if I drive it in 3rd gear? When i drive it in drive the rpm's frop really low when I let off the gas and has to rev back up to 3k rpm to have power. If I drive it in 3rd it doesnt do that. Any information is appreciated.
tblake
11-04-2010, 07:22 PM
I hate to say it but it sounds as though you stripped your 4th clutch shaft splines. Nothing short of a complete rebuild is going to fix the issue.
On driving it in 3rd, if you dont mind filling up every 150-200 miles, then its your call. I don't think you're going to do much more damage to it than has already been done.
On driving it in 3rd, if you dont mind filling up every 150-200 miles, then its your call. I don't think you're going to do much more damage to it than has already been done.
Blue Bowtie
11-04-2010, 07:24 PM
Does the car start from a dead stop in 1st? If you place the selector in manual 1st does the car move? If 1st doesn't operate reliably and 4th doesn't operate it could be a problem with Solenoid A. Failure of the solenoid to operate could be due to the solenoid itself, the electrical connector at the transmission, or the PCM quad driver module. The solenoid can be diagnosed by measuring resistance at the transmission electrical connector (externally) without much difficulty.
It could also be a problem with the OD clutch not operating. It is the outermost clutch in the stack and has only two clutch plates. It may be more prone to slippage because of the reduced surface, especially if the line pressure is low. Low line pressure can result from low fluid level, a clogging filter or leak at the filter pickup tube O ring, a worn or sludged pump, or a sluggish/failing PWM solenoid in the valve body. Line pressure can be tested externally by connecting a pressure gauge to the test port and operating the transmission.
A third gear sprag clutch which is sticking and not releasing can also prevent OD from locking in. This would likely only be caused by contamination of the roller clutch.
A check ball in the valve body could also have worn through the separator plate, and that can also be diagnosed by a line pressure test with the transmission operating.
Further, two valve spools in the valve body must shift to lock in OD, and contamination can prevent their free movement.
As you may be able to see, clean fluid at the right pressure is critical for both hydraulic operating pressure and mechanical lubrication. Clean fluid also helps keep contaminants from accumulating in areas where it can cause problems, like pumps, valves, servoes, and solenoids. If the trans oil and filter have not been serviced lately, it might be a good time to begin with that. Avoid the suggestions to have the transmission "flushed" and only drain the pan contents to replace the filter, then refill with clean Dexron VI.
It could also be a problem with the OD clutch not operating. It is the outermost clutch in the stack and has only two clutch plates. It may be more prone to slippage because of the reduced surface, especially if the line pressure is low. Low line pressure can result from low fluid level, a clogging filter or leak at the filter pickup tube O ring, a worn or sludged pump, or a sluggish/failing PWM solenoid in the valve body. Line pressure can be tested externally by connecting a pressure gauge to the test port and operating the transmission.
A third gear sprag clutch which is sticking and not releasing can also prevent OD from locking in. This would likely only be caused by contamination of the roller clutch.
A check ball in the valve body could also have worn through the separator plate, and that can also be diagnosed by a line pressure test with the transmission operating.
Further, two valve spools in the valve body must shift to lock in OD, and contamination can prevent their free movement.
As you may be able to see, clean fluid at the right pressure is critical for both hydraulic operating pressure and mechanical lubrication. Clean fluid also helps keep contaminants from accumulating in areas where it can cause problems, like pumps, valves, servoes, and solenoids. If the trans oil and filter have not been serviced lately, it might be a good time to begin with that. Avoid the suggestions to have the transmission "flushed" and only drain the pan contents to replace the filter, then refill with clean Dexron VI.
Blue Bowtie
11-04-2010, 07:36 PM
I hate to say it but it sounds as though you stripped your 4th clutch shaft splines. Nothing short of a complete rebuild is going to fix the issue.
On driving it in 3rd, if you dont mind filling up every 150-200 miles, then its your call. I don't think you're going to do much more damage to it than has already been done.
Oh, c'mon. You must be exaggerating. Is it even possible for this meaty beast of a "shaft" to strip?
http://www.wwdsltd.com/files/4T604thInputTube.jpg
I mean, this massive shaft is at least as robust as a toilet tissue tube, maybe even more so... ;)
I'm just trying to test all the possibilities before opening the side cover.
On driving it in 3rd, if you dont mind filling up every 150-200 miles, then its your call. I don't think you're going to do much more damage to it than has already been done.
Oh, c'mon. You must be exaggerating. Is it even possible for this meaty beast of a "shaft" to strip?
http://www.wwdsltd.com/files/4T604thInputTube.jpg
I mean, this massive shaft is at least as robust as a toilet tissue tube, maybe even more so... ;)
I'm just trying to test all the possibilities before opening the side cover.
grandprixgtx00
11-04-2010, 08:43 PM
^^ haha
4th clutch shaft in 4t65e=junk. If you do need a rebuild, I strongly suggest looking into a hardened 4th clutch shaft
http://zzperformance.com/grand_prix/products1.php?id=151&catid=105
good luck!
4th clutch shaft in 4t65e=junk. If you do need a rebuild, I strongly suggest looking into a hardened 4th clutch shaft
http://zzperformance.com/grand_prix/products1.php?id=151&catid=105
good luck!
BNaylor
11-05-2010, 05:53 AM
The 4th clutch shaft is a known problem area but I still have all my originals.
The main symptom of a bad 4th clutch shaft is it will work fine in automatic until it upshifts to 4th (OD) and then it will feel like the car is in neutral until you take it out of OD like manually back to 3rd, 2nd or 1st gears. Of course you may get over revving until you take your foot off the gas. :lol:
The main symptom of a bad 4th clutch shaft is it will work fine in automatic until it upshifts to 4th (OD) and then it will feel like the car is in neutral until you take it out of OD like manually back to 3rd, 2nd or 1st gears. Of course you may get over revving until you take your foot off the gas. :lol:
MoDoggie
11-05-2010, 10:41 AM
I takes off fine when I put it in Drive it just never shifts to overdrive. It doesnt slip or anything, just doesnt shift to OD at higher speeds. When I let off the gas at higher speeds the rpms drop way down as if I put it in neutral and it has to rev back up to say 3000-3500 before it has any power to the wheels again. I will try putting it in 1st like suggested to see if there is any problem there, but like I said it takes off fine and shifts smoothly from 1st to 2nd and from 2nd to 3rd.
tblake
11-05-2010, 10:53 AM
The 4th clutch shaft is a known problem area but I still have all my originals.
Mines original too Bob, and creeping up to 160,000 miles, I'm starting to get a little afraid.
Is there anything that can be done to be as easy on the splines as possible? I never floor it in OD, and when its about to shift into OD, I always back off on the throttle a little.
To the OP, that sure sounds like a stripped 4th clutch shaft to me. Put your trans in "3", get up to about 50-6omph, and maintain speed, and then move the shifter into "D". If your RPM's dont drop, your 4th clutch shaft is stripped.
Mines original too Bob, and creeping up to 160,000 miles, I'm starting to get a little afraid.
Is there anything that can be done to be as easy on the splines as possible? I never floor it in OD, and when its about to shift into OD, I always back off on the throttle a little.
To the OP, that sure sounds like a stripped 4th clutch shaft to me. Put your trans in "3", get up to about 50-6omph, and maintain speed, and then move the shifter into "D". If your RPM's dont drop, your 4th clutch shaft is stripped.
MoDoggie
11-05-2010, 11:05 AM
I've done that and the RPM's do not change. Sounds like it's stripped to me.
BNaylor
11-05-2010, 02:22 PM
Mines original too Bob, and creeping up to 160,000 miles, I'm starting to get a little afraid. Is there anything that can be done to be as easy on the splines as possible? I never floor it in OD, and when its about to shift into OD, I always back off on the throttle a little.
Probably not TIm short of replacing the shaft or getting a tranny rebuild. The latter being better. In this case I'm not sure the 4th clutch shaft is the sole issue since there appears to be no indication an upshift to 4th is occurring. Other issues can cause that. Most common being a defective TFT sensor. Remember it will delay or inhibit shifting to 4th until the tranny temp reaches a certain temperature. Maybe a trans scan is in order especially since many of those DTCs don't set a SES/CEL light.
One thing I'd never do is pull a trailer. 4th OD should never be used if for some reason you do. I recall a member lost his 4th clutch shaft but that was after a cross country trip pulling a UHaul trailer.
Probably not TIm short of replacing the shaft or getting a tranny rebuild. The latter being better. In this case I'm not sure the 4th clutch shaft is the sole issue since there appears to be no indication an upshift to 4th is occurring. Other issues can cause that. Most common being a defective TFT sensor. Remember it will delay or inhibit shifting to 4th until the tranny temp reaches a certain temperature. Maybe a trans scan is in order especially since many of those DTCs don't set a SES/CEL light.
One thing I'd never do is pull a trailer. 4th OD should never be used if for some reason you do. I recall a member lost his 4th clutch shaft but that was after a cross country trip pulling a UHaul trailer.
MoDoggie
11-07-2010, 08:37 AM
Is there a simple way to test the TFT sensor or with the milage should I just replace it to see before having a rebuild done? Im already looking at $1400 for a rebuild so a few more $ isnt a big deal. Is the TFT sensor hard to replace?
Blue Bowtie
11-07-2010, 09:12 AM
The temperature sensor is mounted below the valve body and channel plate. The side cover must be removed to replace the sensor.
The sensor can be tested right at the electrical connector on the transmission, just like the solenoids as I have previously suggested. By simply reading the resistances of the sensor, solenoids, and testing hydraulic pressure, a lot of diagnosis can be done with the transmission still bolted in the vehicle. A scanner will NOT always give you the full story since it relies upon the inputs from the trans through the electrical connector and wire harness. It also requires the PCM to interpret the data correctly, then scale the signals, then output it through the ALDL. Reading directly at the device eliminates all the crap in between and can identify problem within all that crap. As someone here once astutely remarked, the PCM helps identify problems in CIRCUITS, not in devices.
Check the resistance of the temperature sensor between terminals F and G at the transmission. The sensor will present a variable resistance based upon temperature. The resistance scale is somewhat linear between 400K ohms at -40ºC and 0 ohms at 160ºC.
If the temperature sensor is way out of range, open, or shorted, you can install a 1K-10K resistor between the terminals on the electrical connector on the harness from the PCM to "fool" the PCM into thinking the temperature is acceptable, and eliminating the PCM holding off the 4th gear engagement.
While you have your ohmmeter near the trans connector, check the resistance of the shift and PWM solenoids as follows:
Solenoid A - Terminals E and A, 20-30 ohms
Solenoid B - Terminals E and B, 20-30 ohms
TCC Solenoid - Terminals E and D, 20-30 ohms
PWM Solenoid - Terminals E and C, 10-15 ohms
If all this checks out within specifications, drive the vehicle until the transmission is at full operating temperature and test all the resistances again. If everything remains within specs, the problem is likely mechanical or hydraulic, and not the transmission controls. However, if a solenoid does go out of range, the chances are greater that a control problem exists.
Similarly, you can ground the terminals A and B (just like the PCM does) to operate the shift solenoids, but would need to be extremely careful to do this in the correct sequence while driving to prevent serious transmission damage.
A decent transmission shop would do all of this for you as part of a diagnosis, instead of just plugging in a Tech II and handing you an estimate for a replacement transmission as far too many tend to do.
The sensor can be tested right at the electrical connector on the transmission, just like the solenoids as I have previously suggested. By simply reading the resistances of the sensor, solenoids, and testing hydraulic pressure, a lot of diagnosis can be done with the transmission still bolted in the vehicle. A scanner will NOT always give you the full story since it relies upon the inputs from the trans through the electrical connector and wire harness. It also requires the PCM to interpret the data correctly, then scale the signals, then output it through the ALDL. Reading directly at the device eliminates all the crap in between and can identify problem within all that crap. As someone here once astutely remarked, the PCM helps identify problems in CIRCUITS, not in devices.
Check the resistance of the temperature sensor between terminals F and G at the transmission. The sensor will present a variable resistance based upon temperature. The resistance scale is somewhat linear between 400K ohms at -40ºC and 0 ohms at 160ºC.
If the temperature sensor is way out of range, open, or shorted, you can install a 1K-10K resistor between the terminals on the electrical connector on the harness from the PCM to "fool" the PCM into thinking the temperature is acceptable, and eliminating the PCM holding off the 4th gear engagement.
While you have your ohmmeter near the trans connector, check the resistance of the shift and PWM solenoids as follows:
Solenoid A - Terminals E and A, 20-30 ohms
Solenoid B - Terminals E and B, 20-30 ohms
TCC Solenoid - Terminals E and D, 20-30 ohms
PWM Solenoid - Terminals E and C, 10-15 ohms
If all this checks out within specifications, drive the vehicle until the transmission is at full operating temperature and test all the resistances again. If everything remains within specs, the problem is likely mechanical or hydraulic, and not the transmission controls. However, if a solenoid does go out of range, the chances are greater that a control problem exists.
Similarly, you can ground the terminals A and B (just like the PCM does) to operate the shift solenoids, but would need to be extremely careful to do this in the correct sequence while driving to prevent serious transmission damage.
A decent transmission shop would do all of this for you as part of a diagnosis, instead of just plugging in a Tech II and handing you an estimate for a replacement transmission as far too many tend to do.
BNaylor
11-07-2010, 05:12 PM
Pic below will give you an overview of component location.
http://i5.photobucket.com/albums/y186/lizzywiz/valvebody2.jpg
4T65E Autotransaxle
http://i5.photobucket.com/albums/y186/lizzywiz/valvebody2.jpg
4T65E Autotransaxle
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