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Diesel Master
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Discussion Starter · #1 · (Edited)
If the problem is electrical then chances are you can troubleshoot the problem yourself. The torque converter has a torque converter clutch. It is this clutch that provides the mechanical coupling from the engine to the transmission.
The Computer commands this clutch through the torque converter solenoid. The TCC solenoid actuates pilot pressure and sends it to the pump. The pump (in short) puts the pressure on this plate that some call a piston.
The Torque converter itself can get way too hot. By design in the automotive industry has the TCC lockup at highway speeds. It increases fuel economy and allows for a mechanical lockup.
There are certain checks you can conduct to determine what is going wrong if are not going into Overdrive mechanical lockup.

I will never recommend modifying the TCC to manually control to when it engages and as to when it disengages. One of the main reasons is transmission protection. There is a reason why the computer takes you out of OD.

The TCC Stands for Torque Converter Clutch. It is a flat disk with abrasive material.

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Pictured below is the TCC solenoid. You will see three bolts. Between the second and the third bolt and down to the edge of the valve body is is the TCC solenoid. It is the smaller of the two. The solenoid to the left is the Pressure control solenoid. Its job is to control pressure as the computer commands it.

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You can check it by using a multimeter when you disconnect the passthrough connector. Check Pins E and S. The resistance is 8 to 12 Ohms. Buy two male and female test leads and keep them. Use the female leads to test the pins going into the transmisison.



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Do understand this check is good for DTC 83. TCC solenoid circuit fault.
It has nothing to do with the TCC solenoid's valve and bore leaking.

There is another check you can do if you are not going into overdrive. It is the Transmission Fluid Temperature Sensor.

DTC 79 is transmission fluid Overtemp. A defective temp sensor will prevent overdrive.
Use a multimeter between pins L and M to check for resistance. The temperature is related to resistance. If found outside the minimum and maximum resistance and NOT in the nominal column then either you have a bad temp sensor or connection in the pan. A skewed sensor is not that uncommon. The computer doesn't know any better but you have to.
You will need an infrared temp gun and a this temperature reference chart. Aim the temp gun at the bottom of the pan while the transmisison is at operating temperature. Compare the ohms with the temperature reference chart.

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Diesel Master
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Discussion Starter · #2 ·
Another Problem associated with no overdrive. Although not the most common it is very well worth mentioning.

Shifting solenoids do pertain to issues with no engagement in Overdrive. This is an example of the 2-3 shifting solenoid. The 1-2 solenoid functions exactly the same way. Both are not interchangeable.






Fluid pressure must be delivered to the Torque converter solenoid and the 4th
gear shifting valve

The shifting solenoids work through electromagnetism. When the check ball seats as commanded by the computer then the fluid does not exhaust through the exhaust ports. You can recognize where these slots are by noticing where the tan hard plastic ends and the metal plate begins.
When the solenoid is activated there is a metal stem that forces the check ball where you see it in the lower part of the picture. This blocks the fluid forcing pressure thus actuating the shift valve. The fluid is blocked at the screen and cannot pass through the screen when the shifting solenoid is engaged.
When the electricity is shut off at the computer then the check ball is allowed to back off. When this happens then the shifting valve returns. No electricity sent means no gear.

The two shifting solenoids will engage like this:
1-2 energized for first gear.
No solenoid for second gear
2-3 energized for third

Both 1-2 and the 2-3 for 4th gear. Yes 4th gear.

Problems with no overdrive can happen because faults associated with these two solenoids.

Corroded, loose, oily connectivity. The computer supplies voltage through one pin.
(Pin E) The easiest place is to check at the passthrough connector.
The computer controls the solenoid through ground. It will switch off by denying ground at the computer.
A leaking O-ring will cause a lack of pressure to build up and shift the appropriate valve delivering pressure to the TCC solenoid or the 4th gear-shifting valve.
A sticking check ball, corroded, worn out check ball will likewise cause similar problems.
A Tech II scanner can let you know the shift times of these solenoids.

A nine-volt battery with soldered leads can tell you if the solenoids are clicking. You can hear them with the pan still up in the transmission. Understand that this simple test will not be able to tell you if the shifting valve is shifting, leaking O-ring. Just connectivity through the pass through connector


Check resistance through Pin E and A for the 1-2 shifting solenoid.
Check resistance through Pin E and B for the 2-3 shifting solenoid.

If resistance checks out then switch on the ignition and check Pin E and a good ground for 12 volts voltage.
 

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Diesel Master
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Discussion Starter · #3 ·
There is a Torque converter solenoid valve. It sends a signal to the torque converter pump. The TCC gets line pressure from a valve that is opened from the TCC solenoid valve so to speak.
Since your transmission has 200Ks on it the problem is likely that the valve sleeve bore has worn. When the Torque converter Solenoid strokes the piston the transmission fluid leaks past when hot. The hydraulic signal get so weak that it will no longer activate the control valve within the pump thus kicking in OD.


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Diesel Master
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Discussion Starter · #5 ·
As it has been noted before there is a speed sensor located at the transfer case. That along with a buffer sends a signal to the PCM letting it know the vehicle's speed (VSS). This signal along with Engine RPM (ESS) AKA Engine Speed Sensor, Throttle Position Sensor (TPS) are the essential signal inputs determining shifting and OD.

A recent thread.
http://www.dieselplace.com/forum/showthread.php?p=4346037#post4346037
 
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