Vehicle- 1993 Dakota reg 4x4 automatic V6 178k.

I already posted 1 other thread about this problem but now I feel I'm really close to figuring out whats wrong with my tranny.

Problem- My transmission will not shift into overdrive in temperatures below 50F degrees. In temperatures higher then 50F degrees my transmission will shift good in overdrive without a problem.

Parts Replaced- So far I replaced my radiator fluid, temp sensor, O2 sensor, IAC, and speed sensor. I might try replacing the TPS next.

My PCM still shows fault code 15 the speed sensor has no signal after erasing a couple other codes. But I'm starting to believe my computer is tricking me about that code because my speed sensor worked fine in the summer.

After replacing so many sensors I think my tranny problem must be a fluid problem. Because it's so cold that the fluid is getting thicker causing my transmission to make a rumble sound and clog.


Does it seem right that it's a transmission fluid problem causing overdrive problems in cold weather?

Do you recommend this product http://synthetic-motor-oil-air-filte...thetic-ATF.htm

Thanks

 

I recommend replacing the speed sensor.

 

Even though I replaced it a year ago you really think I should replace it again? I guess I can go pick up another one and try it out and if doesn't make a difference than I will know it's something else or the harness.

 

What if you drive the truck several miles (and I mean drive it, not idle the truck without moving it)? Will it shift into overdrive than?

The transmission will not shift into overdrive unless the transmission fluid temperature sensor reports that fluid temperature is above a certain temperature. I don't remember what the temperature is (or is supposed to be), and I'm half the world away from all my books.
It could be that sensor is bad, and I don't know where it is.

 

These transmissions don't have their own fluid temp sensors! The computer uses the coolant temp from the ECT sensor. I guess they figure if the engine coolant is up to temp the transmission fluid probably is too.

Have you replaced you thermostat? What temperature are you getting at the gauge? You did replace the 2 prong sensor and not the 1 prong sensor, right?

Try something one of these days... when its really cold out, put a peice of cardboard over the radiator and let the truck heat up to 5-10 degrees over what it typically runs at and see if the transmission still doesn't shift into OD.

If your TPS was bad, you'd be able to tell by how the engine was running, so don't just go throwing money at the issue that you don't need to spend!!

The fluid can't be a problem or more people than you would be having the same issue and the rest of your gears would be acting up. The same kind of valves are used for OD that are used for 1-3.

 

I replaced my thermostat, radiator fluid, and temp sensor a couple weeks ago. My temperature gauge stays a little under the half way point. It was 58 degrees the other and my transmission shifted into O/D then downshifted back into 3rd and kept going back and fourth.

I traveled 120 miles yesterday with the outside temp at 10 degrees and not once did my truck shift into O/D during the trip.

Does that mean anything because something is really faulty.

 

If you got a code for the speed sensor and you reset it and it came back then common sense says some is wrong. Yes the sensor can be bad even if you just replaced it summertime or even yesterday. Things fail. The other thing is it can be a wiring problem in the speed sensor circuit. A new speed sensor will be the easiest way to find out.

 

I was half right. So do I get a little credit?
It applies only to the 1996 Dakota's. (See 1996 Dakota service manual, page 21-87 "Transmission Fluid Temperature Thermistor"; and page 21-88 "Shift Valve Operation") -- basically on 1996 Dakota, the transmission fluid temp sensor is mounted on the governor pressure sensor; below 50F OR above 250-260F no overdrive or lock-up torque converter)

As per the 1995 Dakota FSM, page 21-88 "Speed, temperature, and throttle position are among the electrical signals supplied to the PCM to operate the overdrive solenoid on the valve body."

Scroll down to page 21-90, and the paragraph "Converter Clutch Control" states:
"Converter clutch engagement in overdrive fourth gear is controlled by sensor inputs to the powertrain control module. In third gear above 25 mph and in fourth gear above 50 mph, sensor inputs to the control module that determine clutch engagement and shift timing are:
- coolant temperature (verifies temperature minimum of 60° F)
- engine speed
- vehicle speed
- throttle position
- manifold vacuum (MAP sensor)"

Please note that with the coolant temperature sensors there are TWO (2) sensors. Both sensors are located on the right (passenger) side of the block.
The sensor that provides input to the temperature gauge has ONE wire. This sensor effects ONLY the coolant temperature gauge on your dash, and has no effect on what the PCM senses as the engine coolant temperature.
The sensor that provides input to the PCM has TWO wires. This sensor provides input to ONLY the PCM and has no effect on the coolant temperature gauge.

Checking operation of these sensors would probably be a good place to start. Does sound like something is messed up.


And yea, I'm going to have to agree with Crazy here -- need to fix that speed sensor error code first. Forgot about that in your 1st post.

 

Mine did this years ago. And I had to put a new sensor inside the trans.

 

Ok James, I'll give you half credit on that. I didn't think about how much more complicated they made the obdii systems. But since your's is the only year they had an obdii 1st gen, some stuff doesn't apply to us low tech obdi guys :P

This is copied from the '96 FSM about your so called thermistor:



But, since the OP has a '93, it doesn't apply. I searched parts sites and through the '95 FSM and nothing is noted about a seperate transmission temp sensor.