I have a 2003 Ranger with 150,000 miles, the 2.3L engine, & what I'm assuming is the 5R44E transmission. I've owned it since it had 63,000 miles on it. Had the transmission flushed around 90,000 & 140,000 miles. Somewhere around 144,000 miles I developed a leak in the coolant reservoir. About 1000 miles later the heater valve came apart while driving. I noticed each incident while the engine was hotter than normal but fortunately before I cooked the engine. I drove a few thousand more miles over the next couple months when the OD light started flashing. As soon as I saw the light flashing I pulled over & cut the engine off. I then checked the fluid which didn't smell burnt but was a dark brown. When I cut it back on the flashing had stopped so I headed for home. After a couples miles the OD light started flashing again. I had to cut the engine off a couple times before I made it back to the house. Once I was in the driveway I took a closer look at everything. The coolant level was slightly low and upon inspecting I found a pinhole leak at the seam in the radiator. I also checked for codes with my cheap reader with no luck. At that point I was hoping the trans had overheated at some point and degraded the fluid enough to trigger the check engine light. I ordered a new radiator. When it came I swapped it out. Then I dropped the transmission pan to change the filter and inspect. There weren't any metal pieces in the pan but there was some of the grey sludge stuck to the magnet. Once I buttoned everything back up I took it for a test drive and still had the same problem.


The transmission seems to shift normally when the OD light isn't flashing. When it is flashing the only symptom I'm getting is a hard shift from 1st to 2nd. Cutting the engine off stops the OD light from flashing. The OD light only starts to flash at speeds over 45 (but not every time). I took the truck to the only local transmission shop with a reasonable reputation. They hooked it up to their Snap-On diagnostic machine and said there were no codes stored. Then they drove it down the road until the OD light started flashing, hooked it up again, and it was showing code P0740. They suggested I check/clean all the electrical connections to the transmission as a first step. No charge for pulling code and bring it back if connections were ok. The OD light didn't flash again for several days. A couple days ago it started flashing again. I pulled/cleaned all the connections this morning. I also followed the wires as far as possible looking for obvious damage. I didn't see anything unusual. I'm hoping someone can point me in the right direction.

 

Welcome to the forum

The OD light is the CEL(check engine light) for the transmission, it is also used to tell driver if OverDrive was turned off by the driver, on steady, when pulling a trailer or hauling a heavy load in the bed you would want to turn OD off, or sometimes if climbing a longer grade and it was shifting back and forth from 4th to OD, turn OD off so it stays in 4th

A transmission code is not always set when OD light flashes, it has to be repeated a few times for the computer to set a code

Look up ALL related codes, never just look up the ONE code the computer used, look at the computers possible choices
P0740 Torque Converter Clutch Circuit Malfunction
P0741 Torque Converter Clutch Circuit Performance or Stuck Off
P0742 Torque Converter Clutch Circuit Stuck On
P0743 Torque Converter Clutch Circuit Electrical
P0744 Torque Converter Clutch Circuit Intermittent

TCC solenoid is how the computer locks the torque converter so it doesn't slip, this gives you better MPG, the computer knows the engine RPMs and it knows the transmissions main shaft RPMs, when torque converter is Locked they should be the SAME RPMs, if not then TCC solenoid is not working correctly

So there are 5 "choices" the computer can use for TCC solenoid problems
It didn't use "stuck on", it didn't use "stuck off", it didn't use electrical, it didn't use intermittent
It used Malfunction, which means TCC solenoid is not staying Locked after activation, i.e. engine RPMs and transmission RPMs do not stay the same
So OD light will flash when that happens, then stop flashing when RPMs are the same again

The dark color fluid means something inside is Slipping, clutches or bands(brakes), torque converter is suppose to slip when it is unlocked or engine would stall when you stopped

You would get P0743 Torque Converter Clutch Circuit Electrical, if solenoid was bad, but it could just be weak, so electrical circuit is OK but not able to hold valve fully closed, which is why the trans shop guy recommended cleaning the terminals, to make sure TCC solenoid was getting a good ground.
(all the transmission solenoids, share the same 12volt fuse power, computer GROUNDS a solenoid to activated it, so dirty ground connection would weaken solenoids ability to stay closed)
And could be the TCC valve is dirty, preventing solenoid from closing passage off completely
Torque converter itself could also be the problem, not staying locked, this could darken fluid

No I don't think the engine cooling system would cause this.

 

Thanks for the information. I had pretty much decided the overheating wasn't related to the transmission issue. Mentioned all that because more information always seems better. I want to make sure I understand what you are saying. The torque converter itself could be bad. The TCC solenoid is too weak to do it's job or some sort of debris is keeping the circuit from closing. It sounds like it's also possible that the speed sensor that detects transmission rpm is not working properly. I'm not sure where to go from here. I don't want to throw parts/money at it hoping to fix the problem. On the other hand, replacing the (external) speed sensor and/or the TCC solenoid is fairly cheap and relatively easy. Any suggestions?

I appreciate the welcome to the forum. I joined back in 2011 when I bought the truck but haven't been back since.

 

Yes, you are understanding it
No, the speed sensor is for drive line speed

The "Malfunction code" would mean the engine RPMs and Transmission Turbine shaft speed(TSS) are not the same all the time when computer has Locked TCC solenoid
Engine RPM sensor or TSS sensor could be at fault although either would set its own code which isn't seen
Changing TCC solenoid may fix it, but would expect a different P074X code if it was the problem, i.e. electrical or stuck code

Yes, could be some Gunk in the valve body, like you found in the pan, that is blocking/limiting flow in passages.

There is no "that is the problem" with available information, and not sure there is a way to do further testing to pin point it better

 

That's exactly the problem. Not enough available info to identify the issue and no good way to test further. I hate to throw money at it in an attempt to find exactly what is causing the problem. With this mileage, age, and transmission problem it may make more sense to sell as is and find another vehicle...….but without knowing how much it will cost to fix I can't make that decision.

 

Yes, a 15 year old vehicle will have its issues, Rangers tend to last longer than most, but like any used vehicle they will have failing parts

I would sell it sooner than later because automatics tend to go downhill fairly fast when there is a noticeable problem