QuestionQUESTION: I have an 04 Dakota quad cab with the 4.7L V8. I am having trouble with the transmission. When I put it in gear it often takes several seconds for the transmission to engage. This most often happens when it hasn't been driven for a few hours. The truck has also refused to shift into overdrive at highway speed on two occasions. Both times this has happened, the check engine light has immediately come on. I took it to autozone and had the codes read. Both times the code was P0700 and P0750. I took the truck to a reputable transmission shop and they found nothing wrong with the transmission. They told me to take it to the dealer because the problem is an electrical control problem that needs to be diagnosed. Do you have any input or advice?
ANSWER: Hi Steve,
That 0750 code says that there is a problem with the low/reverse clutch solenoid. It is either not responding when called upon or the sensor that determines whether it is responding is faulty as regards wiring to it. The two wires you might check are a tan/yellow that runs between pin 14 of the multipin plug at the transmission solenoid assembly to pin 29 at the green multipin plug at the powertrain controller (pcm), and also a light green wire that runs between pin 2 of the assembly to pin 10 of the same pcm plug. Check those wires for continuity between the listed pins, and shake the harness while you do it to check for an intermittent.
Other than that, the solenoid/pressure switch for the L/R reverse clutch may be hanging up which would require removal and servicing of it, or commonly replacing the whole assembly.
Lastly would be the possibility of a defective pcm.
The symptom you describe of slow engagement could well be related to the delayed response of the L/R solenoid, but not the symptom of failing to go into overdrive (the 2/4 clutch and its solenoid are needed for that engagement).
Have you checked the fluid level? Have you smelled to see if the fluid is burnt, or off-color? If you find an issue like that you could try filling to the proper level, or powerflushing all the fluid out and refilling with ATF +4 fluid.
Please let me know if you resolve the issue and how.
Roland
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Roland
---------- FOLLOW-UP ----------
QUESTION: It seems strange that the code I am getting doesn't seem to relate to the overdrive problem because, the best I can tell, the check engine light came on when the overdrive failed to engage.
Does one valve control shifting into both 1st and reverse? It feels like it just slowly engages then clunks into gear. This happens when putting it in both drive and reverse.
Once it is engaged the transmission seems to work fine - except for the 2 times the overdrive would not engage.
I have not changed the fluid in a while but on the dipstick it is full and looks clear/red like it should.
I will check the wires you mentioned and see if I can find anything. If you think of anything else, let me know.
Thanks!
AnswerHi Steve,
As the name implies, low/reverse is needed for both low and reverse gears. A second clutch is needed for both as well but it is different: for reverse you need the reverse clutch and for drive 1st gear you need the underdrive clutch. But the L/R is needed for both of those gears. It may be that you just have a solenoid pressure switch that is lazy or dirty but you would need to remove the solenoid pack to check that out. But the 0750 says that the tcm doesn't 'see' the inductive spike feedback from the solenoid when it sometimes tries to activate it. That could be the wiring or the solenoid itself.
Roland
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