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2006 gmc envoy_denali
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Discussion Starter · #1 ·
I am planning on installing a tranny cooler in the very near future. I would really like to have an idea what temp the fluid is running at. However I don't want to put a gauge in the cab (no where it would go nicely). Is there any point in splicing one under the hood, into the tranny line from the cooler to the existing transmission lines? Would it give any kind of accurate reading about towing temps or running temps considering the time it would take to stop, lift the hood and read the gauge or would it always cool down to quickly to get a reading? So much information on this site it I am always.
 

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2005 chevy trailblazer_lt
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434 Posts
You need to splice it into the line between the transmission and the first cooler. You want the temperature from the torque converter, where the heat occurs. You could hide it in the center console.
 

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2006 gmc envoy_denali
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Discussion Starter · #3 ·
Thanks Double D that makes sense to get it in before the first (radiator) cooler. Hadn't thought about the center console since it has so much other junk in it. Do you think it will hold the temp for a couple of minuets after stopping?
 

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2009 gmc envoy_slt
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153 Posts
You could also try a ScanGauge (trade name). It plugs into the OBDII port under the steering column. You have to program it a bit to get the Tx temp. The gauge is pretty small and gives other info as well - like Engine Oil temp, fuel consumption, HP and reads fault codes etc. I did this with mine and installed it on the front left dash just by the door above the air vent. Look up www.scangauge.com or try searching for a Canadian dealer - I think Gifford or something like that has them in Canada - about $170 - and a whole lot easier than splicing one in under the hood.
My 2 cents.
 

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2002 chevy
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83 Posts
I would recommend to install the sender unit in the tranny pan to get a fair reading.

I did install a temp gauge on my old Crysler T&C on the outgoing cooler line, not good.
The only thing that would give you is a heart attack, the temp is going to be very high at some times and according to a tranny rebuilder i know that temp isn't interesting anyway.

You will get a more accurate and even reading on what temperature the fluid has going in to the pump, wich is the most correct way to gauge the temp.:m2:
 

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2009 gmc envoy_slt
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You could also try a ScanGauge (trade name). It plugs into the OBDII port under the steering column. You have to program it a bit to get the Tx temp. The gauge is pretty small and gives other info as well - like Engine Oil temp, fuel consumption, HP and reads fault codes etc. I did this with mine and installed it on the front left dash just by the door above the air vent. Look up www.scangauge.com or try searching for a Canadian dealer - I think Gifford or something like that has them in Canada - about $170 - and a whole lot easier than splicing one in under the hood.
My 2 cents.
Is the transmission temperature sensed on all Envoys? I just bought a Scan Gauge and tried the VPW code with no luck. Used the CANSF code and get a reading of 32F. Would be glad to find a link to the codes you programmed into the Scan Gauge.
 

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2009 gmc envoy_slt
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I would think the Tx temp is available on all Envoy's - but not sure. There is a page on the Scan Guage web site (also see below) and it gives the codes. I had to use the Cansf codes and used the Allison Tx to get it in Deg F only.
Try this link:
http://www.scangauge.com/support/pdfs/XGAUGE.pdf

I used the following code to get my Tx temp:
Allison Transmission Fluid Temperature 07E2221940(01) 046205190640 3008 00090005FFD8 TFT Degrees F
 

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2009 gmc envoy_slt
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Thanks Brian,

The Alison code worked. I am now reading 84 F after setting in my driveway all afternoon, which makes sense. Thanks again for the prompt reply. To all others, the Scan Gauge is an excellent way to monitor HP, torque, A/F, O2, ...
 

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2002 chevy trailblazer_ltz
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i have a Scangauge too, but 84F, are you sure? because i am constantly monitor my Transfer temp, it always stick between 160F and 180F and some times it go up to 210F after a long ride, my trans is already rebuild, and the trans oil new.
 

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2009 gmc envoy_slt
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I'm guessing the 84F is roughly the ambient air temp after the vehicle has been sitting in the driveway for the afternoon - the oil cools to ambient temp. I get the same with that scan code - the engine oil temp and Tx temp match the ambient air temp after sitting. Them once you take her for a spin, the temps go up. My oil temp regularly reaches 200 F but the Tx Temp runs between 140 - 170 F with normal temp seeming to be around 150F. Ambient air is about 65-70F. A little cool I think (I have a cooler with an internal bypass) and will watch the temp in the winter. I want it warm enough to 'cook' out the moisture. I may install a manual valve to bypass the cooler completely to ensure it warms up enough. I pull a boat once in a while and notice that using 3rd instead of Drive does keep the temperature lower.
What are others getting for a Tx temp without a cooler?
 

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2009 gmc envoy_slt
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Envoy Trans Temp.

Shdamaj, Brian K

The 84F was after setting in my driveway for a few hours. What Brian K reports is very close to my experience. I have not yet towed a heavy load, but have seen up to 180F on steady expressway driving, medium passenger load. If my experience when towing gets the temp up over 200 F, I will likely add the cooler in front of the radiator.

Brian's thought on being able to isolate the cooler in the winter is a good one. I am thinking of a three way valve, in the line running from the factory radiator cooler to the added cooler. The three way valve would allow:
1. Flow straight through for majority of the year, thereby using the added cooler.
2. The third port would close off going to the added cooler and send the trans fluid through what is essentially a tee connection to another tee connection on the line that sends coolant back to the transmission, thus bypassing the added cooler. This would put you right back to only using the factory radiator cooler.

I had a previous Envoy, bought used and I had to get the tranny rebuilt on it. This is why with my new 09 I became interested in the Scan Gauge, so I know what is going on.

If you are in a hot climate, with long hill climbs, the 210F is likely accurate. Further, if you don't have winter like we do in the Northeast, I would definitely get the added cooler. Hope this helps.
 

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2002 chevy
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Trans. Temp guage on my dashboard

The idea of using a code readout seems nice, and multi-purpose. Since I did not know about them 5 years ago, I just put in a gauge. In case you (or others) are thinking of that, here are two pics of the transmission temperature gauge I mounted on my dashboard. I used sticky-back velcro so the annual inspection mechanic could move the gauge to get at the stickers. It does not look bad, IMO (but then, I'm an engineer with a function-over-form mindset :).

I placed the sensor in the outgoing line TO the radiator. Don't have any extra, aftermarket cooler. Tow a camping trailer in summer, seldom get temp.s in the yellow (that's about 220 degF going TO the radiator). I do change all 12 or so quarts of fluid every 2 years.

Hope this helps!
 

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2002 chevy
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Transmission cooling line diverter?

I'm also thinking of putting a diverter/drain valve in the return line, just before coolant goes back into the tranny, to make fluid replacement easy for DIY (had shops do it in the past).

If anyone has found a one-piece diverter, please post details. I don't want to hang a pound of brass fittings on the line!
 

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2002 chevy
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photos of sensor in cooling line

This is an update to my post above with photos of my dashboard guage. These show the hookup in the transmission cooling line. I chose to put the sensor in the HOT line going TO the transmission. I wanted to see the highest temperatures that the fluid experiences. (I should have included these with the original post.) These photos were taken about 3000 miles after re-doing the lines. (I had the cooling line rust through problem, separate threads on this site.)

Update to my original post: I installed an aux transmission cooler this past summer.

Photos show how poorly compression fittings do in this application. (It came with the guage kit.) If it gets any messier, I will look for a better way...
 

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2006 chevy trailblazer_lt_ext
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I would have though the compression fittings would have been fine . Nice to know that you have had troubles
 

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2002 chevy
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compression fitting issues

fire06: The troubles experienced by myself and others with compression fittings in the transmission cooling lines are described in other places on this forum:

Transmission cooling line replacement (due to rust through issue):
http://forums.trailvoy.com/showthread.php?t=74948

Installation of auxiliary transmission fluid coolers. There are multiple threads on the subject, lots to read. Here's one to start:
http://forums.trailvoy.com/showthread.php?t=73742

If I recall correctly, the trouble stems from the heat-up and cool-down each time the vehicle is used. The brass fitting and its ferrulls (rings) are a different material than the steel lines. The metals expand differently. Over time, this is thought to cause the leaking. Just tightening it risks stripping threads or twisting the steel line. When I tried tightening my fitting a few years after installing on the old, original lines, the line twisted, cracked and leaked more. I understand flare fittings are better, but a tool is needed to make the flare on a line you cut into.

HTH,
Vic
 

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I bought a flaring kit from Schucks when I installed my aux trans cooler for my 02, havent had any leaking from the flares but where the flexible line connects to the cooler itself I get a little bit of oily dirt accumulation after a year or so.

GarbeVic, you see 220F+ when towing in the summer? 220F is bad, unfortunately Im betting ALL TVs experience temps this high when towing in the summer. I bet after the aux cooler you never see about 200-205F even when pushing it, know my temps dropped ~20F while towing and ~20-30F while normally driving around.
 

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2002 chevy
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Tranny coolant temp.

ScarabEpic22: My 220 degF is on the OUTGOING line TO the radiator and aux. cooler. I gives the hottest temperature in the system. I did that on purpose, because I read somewhere that if the fluid ever experiences temperatures above 250 degF or so it will burn. Getting the temperature of the burnt-then-cooled fluid seemed less useful. If the actual burn temperature is not 250 degF, someone please post the correct value.

BTW, just today i ordered the ScanGuage II OBDC code reader that others have mentioned. If I had known of it 6 years ago, I would not have done the dashboard gauge. So now I will be able to get both temperatures: before cooling (on the dashboard gauge) and after cooling going back into the transmission - I think that is what the OBDC II reader will give me. If anyone knows better, please post.
 

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2009 gmc envoy_slt
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Please let us know what you find out. I would assume that the GM temp probe would be in the body of the Transmission 'somewhere' and not on a cooler line (either the outlet or return) and would give a fairly representative average temperature reading that I suspect is a hotter reading than the outlet of the cooler/rad and more likely closer to the the inlet to the coolers - but I'm just guessing. To be sure you're interpreting the data correctly you will have to try to verify the accuracy of the 2 devices - the GM sensor via Scanguage and your Dash Guage. Mine (Scanguage) pretty accurately reads ambient temp when the Tx is cooled overnight so at least one point on the temp curve is relatively accurate. If GM uses the same sensor as Water Temp I'd be confident that it is relatively accurate as the Water Temp seems reasonable - although it is way different than the Dash water temp guage (which we understand is horribly inaccurate). There are postings here for accessing the Tx Temp using Scanguage (use Allison code if I remember correctly) and their web site is pretty good too.
 

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2006 chevy trailblazer_ls
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The temperature sensor is integrated in the manual fluid valve/switch mounted on the underside of the valve body. It simply sits in the fluid in the pan.

If you're looking for the maximum temperature the fluid reaches, use a sensor on the cooler line exiting the transmission. If you want the temperature of the fluid the transmission is pulling in to function use the factory sensor through OBD.
 
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