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Help find Tranny Temp Sensor

21K views 15 replies 5 participants last post by  Ruderunner 
#1 ·
Our 92 D250, a518 has been bouncing in and out of overdrive. We took it to a Dodge dealer for diagnostic. They said we need a new Transmission Temperature Sensor/switch (part# 56026720). The dealer is unable to find one, I have been making calls for the past two weeks, checking Parts places, online sources, and salvage yards. I have not had any success. I was hoping someone here would be able to help me find one or tell me if there is another sensor/switch that will thread, plug in, and operate correctly (even with some modifications). ANY help at all would be greatly appreciated.
 
#2 ·
Are you sure they ment temp sensor and not TPS? I didnt think the 46re had a temp sensor and wouldnt understand why it would have any thing to do with overdrive? Before i converted mine to standard trans i replaced the TPS with a potentiometer and it made a world of difference on how the overdrive shifted
 
#3 · (Edited)
First gens do not have a Trans Temp Sensor. Your description does sound like you have a failing Throttle Position Sensor, or TPS. It is a common problem for both first and second gen trucks. Many people replace the sensor with a potentiometer. There are aftermarket kits for that, or you can make one yourself with a little know how.

Edit: I stand corrected. A consultation to the FSM and I proved myself wrong. What you have there is called a "Diesel Thermo Switch" in the manual. There are two specific to our A518. The first is the engine coolant temperature switch, which prevents OD operation when engine coolant temps are below 65F. You have the transmission fluid temperature switch, which prevents OD operation when the transmission fluid temperature in the outlet cooler line exceeds 270-275F.
 
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#5 ·
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#6 ·
The dealership took the part out of my truck and took this picture of it, can anyone identify it if it isn't a temperature sensor?
We have bypassed the TPS in the past but were still having issues with OD. The battery indicator in the dash was jumping around even after buying a new altrenator so we bought a new PCM that the dealer had to flash so we hooked the TPS back up and took it to the dealer. The dealer installed/flashed the new PCM we drove it for a few days and the OD issue was worse than before so we took it in for diagnostic. The dealer said the problem is the transmission temperature sensor is sending erratic signals to the PCM. ???????
 

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#7 ·
That lloks more like a pressure sensor. Temp sensors will have a probe the looks like a solid tube hanging of of the inner side of the sensor. I think the reason why you cant find the part anywhere is because your giving the parts guys mis info. Id take the sensor to a good trans shop and let them have a look. Dealers only have trianing on newer vehicels these trucks are two decades old
 
#8 ·
that is a Trans temp switch mount's in the lineright under bell housing on the 518 auto's send me a PM I can help you out .
 
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#9 ·
I edited my earlier post to include updated information. Simplysmn is right, and that is a trans temp switch. It is discontinued, so used is your best bet for now. I haven't been able to cross-reference the PN to anything newer. Val is a good guy to do business with, I would talk to him for sure :thumbsup:
 
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#10 ·
Thank you DieselPunk for the edit and additional information. Does your FSM show any technical specs for the "Diesel Thermo Switch"? ... Maybe I can find another thermo switch that fits the same paramiters.??
 
#12 ·
No technical specs unfortunately. Try googling your issue, someone may have found a fix that works. And give Val some time, he's had it rough the past few weeks with his Durango and all!
 
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#13 ·
I got a reply from simplysmn. He has a used one, I look forward to doing business with him. Thank you DieselPunk for taking the time to help out. I did Google my issue and didn't find any definitive answers. For anyone else reading this who knows where I can get an unused one I would be grateful for the information.
 
#14 ·
That switch is just that, a switch. It's either open or closed based on trans fluid temp, but right now I 'm not sure if it's open or closed when the temp gets too high.

Diagnose it your self, pull the connector off, drive the truck, if od styas enggaged or doesn't ever engage you're onto something. Now jump the terminals, does the truck not engage or always engage (should be opposite of previous test)? if so the sender is bad, you can do a permanent bypass if you can't find a replacement switch.

If operation is still erratic during weither of the above tests, the problem lies elsewhere. Most likely a TPS problem.
 
#15 ·
We just went and got it from the dealership where it has been sitting for the last 3 weeks. They had taken the sensor out and put a plug in the hole we drove it home that way, there is no overdrive at all. We used a small piece of wire and jumped the the wires where the the trans temp sensor plugs in, to close the circuit. We have overdrive with it this way. I would rather not leave it short circuited like that though. Still need the sensor.
 
#16 ·
Not necessarily. The sensor is there to force the trans out of overdrive if fluid temps get too high. This pretty much only happens when towing heavy loads and can crutched by kicking off od when pulling grades and such.

That said I appreciate folks who try to keep things functioning as designed.
 
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