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Old 11-12-2011, 09:58 AM   #1
Bill
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Default RV Tech Tips article on transmission temperature

http://rvtechtips.blogspot.com/2011/...mperature.html

Do you know your transmission temperature? My Explorer, rated at about 7000 pounds, has a big auxiliary transmission cooler as part of the tow package. It seems to be thermostatically controlled at about 180 degrees when driving with no load. When pulling the TM on the flats on a cool day, it will stay there. But it doesn't take much in the way of hills to get it to 190-195 degrees. I have an alarm set at 200 degrees, and I NEVER let it exceed 220 degrees, even for a minute, even when climbing the steepest hills on the hottest days at the highest altitudes.

I went through a transmission repair once, and it was a ghastly experience. I hope never to do it again.

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Old 11-12-2011, 06:09 PM   #2
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Quote:
Originally Posted by Bill View Post
]I have an alarm set at 200 degrees, and I NEVER let it exceed 220 degrees, even for a minute, even when climbing the steepest hills on the hottest days at the highest altitudes.
What alarm do you use? OEM, inline, Scangauge, etc.?

Interestingly, I've been on this same subject in recent weeks. I also found this collection of reference images that is interesting:

http://kamperbob.com/images/TransTempChart.html

I have trying to ascertain whether the Scangauge will monitor ATF temps on our Sequoia. Most folks on the Toyota forum say they haven't gotten it to work (on late model Sequoias and Tundras) and when I contact Scangauge directly, they say it "probably will work", but oddly enough, it sounds like they have not tested it.

In any event, assuming it doesn't, I'd like to find an easy-to-install monitoring device. And then to figure out where exactly to install it, as temps vary widely depending on whether or not the sensor is in a line vs. the pan, cooler line vs. return line, etc.

Dave
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Old 11-12-2011, 10:01 PM   #3
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I can confirm that the ScanGuage will not measure trans temp on a 2005 Tacoma...
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Old 11-12-2011, 11:07 PM   #4
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Scott - Scangauge's response to my inquiry was that "there's a good chance" it would now monitor ATF temp on 05 and later Toyotas using this XGauge:

Transmission Fluid Temperature
TXD: 07E021D9
RXF: 032180000000
RXD: 2810
MTH: 00070065FE70
NAM: TFT

But that's not exactly a vote of confidence. It's great if I get a temp display in the unit, but I personally will have no way of knowing if it actually represents the ATF temp. Do you remember if you ever tried it?

This same XGauge is posted here, so that is encouraging:
http://www.scangauge.com/support/toyota-specific/

...but someone on another forum reported it didn't work on the 06 Tundra. But you might try it on your Tacoma if you haven't already. Maybe its computer is slightly different and it would work.

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Old 11-13-2011, 09:42 AM   #5
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Dave - those are good images, better than the ones I have posted in the past. And they all seem to say about the same thing. Thanks for the link.

As it happens, I use an Aeroforce Interceptor. When I bought, it was about the same price as a ScanGauge, was better looking, but displayed only two parameters at a time, whereas the Scan Gauge displayed four. The choice is yours, of course.

It is probably important to realize that these "gauges" don't actually measure anything. What they do is read and display whatever information is on your vehicle's computer data bus. If some parameter (like transmission temp) is there, the "gauge" will display it, because they are designed to be able to display everything. If the parameter is not there, the gauge cannot create it. So when the gauge manufacturer says "Our gauge probably will measure tranny temp", what he is really saying is "Toyota probably puts the information on the computer bus, but we have no way to be sure". So when you get an answer like this from any of the gauge manufacturers, the next step is not to harangue him - he has no control over it - but to try to get the info from Toyota or one of its technical web sites.

As for the location where the measurement is actually made (pan, cooler, etc)? I'm not sure you will ever figure out the exact location. My feeling is that I don't really care where it is made. I have faith that the measurement is made somewhere that is meaningful to the car's computer - otherwise, why measure it at all? What I watch for is a change from the baseline. In other words, I don't really care whether the initial reading is 175 or 185. What I look for is a 20 degree rise, or a 40 degree rise, from the baseline.

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Old 11-13-2011, 10:03 AM   #6
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Good information Dave. Last time I checked (probably a year or so ago) I didn't find this and an email to ScanGuage got a negative response. I'll give it a try and report back... Edit: Just discovered I need a firmware update, so my test will not be for awhile!
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Old 11-13-2011, 10:56 AM   #7
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As it happens, I use an Aeroforce Interceptor. When I bought, it was about the same price as a ScanGauge, was better looking, but displayed only two parameters at a time, whereas the Scan Gauge displayed four.
That is good to know, as I had not known about the Aeroforce, so I will definitely check it out. One thing I did notice is that the Scangauge display resolution is very poor -- I don't understand that.

Quote:
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It is probably important to realize that these "gauges" don't actually measure anything. What they do is read and display whatever information is on your vehicle's computer data bus.
Yes, I realize this. But from reading the forum posts (including some from Scangauge), the problem doesn't sound like it lies in the fact that the vehicle does not provide this information on the data bus. The problem sounds more like Scangauge has not figured out how to read it. My vehicle has some sort of ATF sensor, as there is a dummy light on the dash that illuminates when the ATF temp reaches a certain temperature. Of course, maybe this isn't a temperature probe per se, but some sort of relief valve that actuates a switch. But this Scangauge problem is new with 2005 and later Toyotas. Scangauge can read ATF temp on 2004 and older Toyotas, and I can't see them removing that functionality; it sounds like they redesigned the bus architecture or something.

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Originally Posted by Bill View Post
As for the location where the measurement is actually made (pan, cooler, etc)? I'm not sure you will ever figure out the exact location. My feeling is that I don't really care where it is made. I have faith that the measurement is made somewhere that is meaningful to the car's computer - otherwise, why measure it at all? What I watch for is a change from the baseline. In other words, I don't really care whether the initial reading is 175 or 185. What I look for is a 20 degree rise, or a 40 degree rise, from the baseline.
My question here was more about where to install an ATF temperature probe somewhere in the tranny system myself if I cannot get Scangauge or the Interceptor to read it off the OBD bus. To do this, I'd have either drill a hole in the tranny pan and screw in a sensor, or cut out a piece of ATF line to install an inline sensor, and then run a wire from this sensor to a display unit in the cab. That's the only way I know how to get ATF temp if that's the case. But your point about watching for swings or trends relative to a baseline is well taken, and that's probably good enough, and certainly better than no monitor at all.

Dave
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Old 11-13-2011, 11:38 AM   #8
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A possible solution is to contact Toyota engineering. My guess is the temp is on the bus, you just need someone to give you the fetch codes to ask the computer to spit it out.
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Old 11-13-2011, 10:11 PM   #9
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Quote:
Originally Posted by ShrimpBurrito View Post
My question here was more about where to install an ATF temperature probe somewhere in the tranny system myself if I cannot get Scangauge or the Interceptor to read it off the OBD bus. To do this, I'd have either drill a hole in the tranny pan and screw in a sensor, or cut out a piece of ATF line to install an inline sensor, and then run a wire from this sensor to a display unit in the cab. That's the only way I know how to get ATF temp if that's the case.
Dave
Dave - Go way back to the beginning of the board - 2002? - and look for posts by RockyMtnRay on the topic. To the best of my memory, he did the first installation of a "real" sensor and gauge on this board, and ran into a problem finding a shop to do the work. But he ended up with a lot of knowledge, and a good setup.

I will look for the original thread - it may be lost in the archives. A followup is here.
http://www.trailmanorowners.com/foru...ead.php?t=2900

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Old 12-01-2011, 09:16 AM   #10
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Got the ScanGuage firmware updated and set up the XGuage last night as recommended to measure trans temp. Seems to work just fine. My Tacoma is '05, which appears to be the earliest year this will work. Note: the XGuage function confused the heck out of me. But after following the directions to set up a function, it becomes just like any other function and can be displayed without issue. Thanks for the inspiration Dave.
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