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Discussion Starter · #1 ·
Just bought an '03 Chev 2500 4x4 LT (Duramax of course) on Saturday, and I drove it 185 miles to work this morning. I had some problems and I am glad I found this site. This is my first post. I hope someone can help.

After about an hour of driving I noticed that my tranny temp was reading a little high, I think around 250 degrees. Not quite in the red, but close enough to get the hairs on the back of my neck to stand up. It was 4 o'clock in the morning, so the air temp wasn't too hot, and I was doing a constant 80 MPH on flat terrain.

This worried me a little since I was headed to the mountains that separate AZ from San Diego. Sure enough, after about 1000 feet of climbing my tranny temp gauge reads well in to the red. I immediately pull over, put it in park and idle for a while. The temp only drops slightly. I decide to start moving again, but I keep it slow behind some big rigs (around 35-40 MPH). The temp neither drops or rises, but it is hovering right around 300 degrees on the indicator.

I pulled off the road about 3x, each time waiting between 15-30 minutes. Still no significant change in temp. Also, I read in the owners manual that the DIC is supposed to display Trans Overheat... but it never did.

After a few miles I finally make it to a gas station where I sit again for another 20 minutes. I decided to check the fluid levels, and everything looked good. Then it dawns on me to feel the tranny to see if it is hot. The tranny and the filter were only warm to the touch, not hot at all. By comparison, the engine oil filter was very warm, to the point where I couldn't keep my hand on it.

I decide that it must be a faulty gauge and I press on to San Diego. No problems with shifting or anything like that the entire way. My guess is it is a bad Tranny Temp Sensor.

So here are my 5 questions:
1. Has anyone else had this problem?
2. Do you agree it is a temp sensor?
3. Where is the temp sensor located?
4. Is this a dealer only item?
5. Does the DIC get a separate reading from the gauge and is that why I didn't get a message?

Quite a story for a first post, eh? Any help would be GREATLY appreciated. This is my first diesel, and I feel very, very lost right now.
 

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That is very strange that your truck rose past 1/2 way on the gauge. Since you just bought the truck Id atleast get the spin on filter replaced. Its real simple to do just like a oil filter. Your suppose to change then every 10,000 miles. (You could also get the trans fluid changed and the internal filter but those seldom go bad.) If that doesnt help Id take it to someone with a scanner. They should be able to read the trans temp from the monitor. That will tell you if its a bad gauge or sensor. I beleave the sensor is located on the trans pan but could be wrong.

Is the trans fluid still red not brown and burnt?
How many miles are on your truck?



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first off :welcome to the site...i have two trucks but never had a over heating trouble with either one,like it was posted above change the tranny filter and see how the fluid looks and keep the filter changed every 8 to 10k miles...i have 90+k trouble free miles on the 05 lly and the 06 has 42k on her no problems with either one,runnin as strong as new or should i say stronger:fart:drink good luck there and keep us posted on what happens
 

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I would start with a spin on filter change and go from there!

FWIW the trans temp sender is inside the trans pan not a easy change!
 

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Discussion Starter · #5 ·
That is very strange that your truck rose past 1/2 way on the gauge. Since you just bought the truck Id atleast get the spin on filter replaced. Its real simple to do just like a oil filter. Your suppose to change then every 10,000 miles. (You could also get the trans fluid changed and the internal filter but those seldom go bad.) If that doesnt help Id take it to someone with a scanner. They should be able to read the trans temp from the monitor. That will tell you if its a bad gauge or sensor. I beleave the sensor is located on the trans pan but could be wrong.

Is the trans fluid still red not brown and burnt?
How many miles are on your truck?
Thanks for the tips. I will give it a shot. The fluid is still red and does not smell burned.

first off :welcome to the site...i have two trucks but never had a over heating trouble with either one,like it was posted above change the tranny filter and see how the fluid looks and keep the filter changed every 8 to 10k miles...i have 90+k trouble free miles on the 05 lly and the 06 has 42k on her no problems with either one,runnin as strong as new or should i say stronger:fart:drink good luck there and keep us posted on what happens
Thanks for the welcome. I am glad I found this site. There are 91K miles on the truck now. I just picked it up on Saturday. Other than this indication problem, it is a great truck.

I would start with a spin on filter change and go from there!

FWIW the trans temp sender is inside the trans pan not a easy change!
OUCH! Not the news I wanted to hear. I was hoping it would be a quick change. I guess the silver lining is that when I do change the sensor, I might as well go ahead and do everything while I have the pan off. Heck, maybe even buy a bigger pan... Hmmmm.

BTW, what does FWIW mean? I have also seen FTW on other forums and I have no clue.:eek:
 

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Discussion Starter · #7 ·
UPDATE: Today I spent a lot of time and a whole lotta money getting my truck in working order. I decided to go ahead and change my oil while I was under the truck fixing my tranny temp problem. The oil change was the only thing for me that went smooth ($50). Oh yeah, the air filter was an easy change too ($22).

First, NAPA sold me the wrong spin on tranny filter, so I had to go back and get one from the dealer ($30). Then the replacement tranny temp sensor I got from the dealer was the wrong one ($13, returned). It took a while, but I finally got the right part and installed it ($96). Turns out the part is also the tranny pressure sensor. It is in the pan, so I had to drain my system to get to it. No biggy since I planned to do that anyway. But the last bit of fun was the guys at the auto parts store told me my the capacity of the Allison tranny was 8 qts, but it turned out to be 11 qts. I limped back to the auto parts store to get the 3 additional qts with just enough fluid to get me in to 2nd gear. But, that is done now and I now have a working system. At least the dealer sold me the right internal tranny filter ($45).

Of course, now my CEL is on from having too little tranny fluid in it when I started it. Does anybody know how to reset it?
 

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Discussion Starter · #8 ·
Another Update: My problem with the tranny temp indication is still there. That was a load of money wasted on that sensor. Oh well. Time to buy an after market gauge.

I did manage to get my CEL to reset. I just pulled the negative terminals off the batteries for a few minutes.
 

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Another Update: My problem with the tranny temp indication is still there. That was a load of money wasted on that sensor. Oh well. Time to buy an after market gauge.

I did manage to get my CEL to reset. I just pulled the negative terminals off the batteries for a few minutes.
First thing you want to do is check cooler lines at the cooler. When the trans gets hot, reach inside the grill and touch both lines and see if they are hot. They better be. Usually hot temps arise from a bad converter.
 

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Discussion Starter · #12 ·
Latest Update

I have tried several different techniques to fix my tranny temp problem, including changing the sensor unit, openening the gauge cluster, and having the transmission shop run a flow test, and eveything seems to indicate a faulty temp indicator.

I priced oem replacement gauges, and it was too expensive for just one bad gauge, so I opted for an aftermarket trans temp gauge. I figured while I was at it I would also get a pyrometer. I have yet to install either, but hopefully I can put this whole trans temp problem behind me...

Next stop is a new programmer!

Thanks to all who helped.
 

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I have tried several different techniques to fix my tranny temp problem, including changing the sensor unit, openening the gauge cluster, and having the transmission shop run a flow test, and eveything seems to indicate a faulty temp indicator.

I priced oem replacement gauges, and it was too expensive for just one bad gauge, so I opted for an aftermarket trans temp gauge. I figured while I was at it I would also get a pyrometer. I have yet to install either, but hopefully I can put this whole trans temp problem behind me...

Next stop is a new programmer!

Thanks to all who helped.
Have you checked trans temps with a Tech 2? Have you changed the spin on filter? What kind of flow test was done and what specs was that compared to? Sounds like you're just throwing money at the problem.
 
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