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Discussion Starter #1
I am installing an aftermarket transmission temp gauge in my 2003 Range Rover HSE.

I have narrowed down installing the sender for the gauge in the line that runs from the trans to the cooler, or dropping the pan and welding in a bung in the pan.

Anybody have opinions as to which is better?

Anybody know if any of the "test plugs" in the side of the transmission could be removed and a sensor placed in that location to get an accurate reading?

Any help is appreciated!

Thanks!
 

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LEGACY VENDOR
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Jon,

There is an external tapping point on the return path from the cooler – it’s on the RH side of the casing, about half way up, close to where the bellhousing bolts to the intermediate (oil pump) casing - see top of page 3 on the attached document.

However, I believe that the temperature measurement here would be too sensitive to the torque converter LUC application (flow will change significantly when LUC is engaged). I would therefore strongly recommend that you measure the bulk oil temperature in the sump instead. As you suggested, this would probably be best achieved by welding a boss on the side of the sump pan and drilling & tapping it to a suitable size for your new sensor.

The existing fluid temperature PTC sensor used by transmission ECU, which is built into the solenoid wiring loom, also measures the bulk oil temperature.

Phil
 

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Discussion Starter #3
Thanks Phil! I agree that measuring the oil AFTER the cooler would not be ideal.

I was thinking of having a new line made that goes out of the trans to the oil cooler, with a boss in it, but the pan is a better route I think.

I purchased a "used" pan off ebay and will weld a boss onto it. Then, I will have the trans serviced and this new pan installed!

Thanks!
 

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I agree that monitoring the fluid temperature ahead of the cooler would also be useful (though you might frighten yourself!) – clearly what you really need is both temperatures :D

I’m not sure if there’s sufficient room under the vehicle for this but it’s conceivable that you could drill through the face of the banjo bolt, where the fluid leaving the casing enters the cooler pipe, and attach the sensor there?

I had a quick look on Microcat and although the sealing washers either side of the banjo bolt are available as separate parts unfortunately it looks like the banjo bolt itself is only available as part of the cooler pipe kit (i.e. no separate part number). You might be able to source one elsewhere, otherwise you’d have to modify your existing one.

Too risky? Getting the thing to seal properly & have no leaks would concern me the most, I think.

Phil
 

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Discussion Starter #5
Phil,

On the transmission side, the other thought is to cut the line that goes TO the cooler and insert a metal sleeve that has a boss incorporated into it for the sensor. That cooler hose can't be under super high pressure. I won't get the temp directly in the pan, but I will get the temp of fluid heading TO the cooler.

On the Engine Oil Temp side, I am also installing an oil temp sender for an aftermarket gauge. I am having my machine shop build a "Y" adapter that will connect at the oil filter housing where (I believe) the existing oil temp gauge is. I will then install the existing oil temp gauge in one part of the "Y" and the aftermarket sender in the other leg of the "Y". While it would be best to get the oil temp directly from the pan, It's too large of a job to drop the oil pan to drill/tap/weld onto it for a boss. Thoughts?
 

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Yep, I agree with all that. I guess the biggest concern with not measuring at the sump (both engine & transmission) is that the lubrication circuits are under pressure - though, as you stated, not very high - which might increase the chances of leaks. Otherwise, what you're proposing sounds fine to me.

Phil
 

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Discussion Starter #8
I will absolutely allow the cars existing sensors/electronic/warnings do the job as per the design of the car. However, I would rather have more granular information to warn me in advance that I am about to get a "trans overheat" warning.

Since I don't own a testbook or blackbox, and I regularly go 50 to 100 miles offroad, away from civilization, I feel like more information is better. So, if I see the trans temp start to creep up while I am crawling along in deep sand, I can stop and cool the trans before the dreaded "BONG" that makes my stomach drop each time I hear it.

Also, from my race car experience, I have found that often times the "factory warnings" occur just at the point of major problems. For example, it is common for the S54 motor in an E46 BMW M3 to run an oil temp of 300 degrees. No warning bells go off while running around at 300 degrees. However, I don't want my race motors running 300 degree oil temps, so I rely on a programmable dash where I can set the warning temps to my desire. As a final example, the Ford Superduty has a trans temp gauge as factory equipment, but it is a well documented fact that the neddle on the gauge stays in the "normal" zone with tranny temps from 100 to 235 degrees. It only starts to move toward the hot zone at 240 degrees and by the time the needle is in the red, the trans temp is 255 degrees. It's a common belief that 255 degrees is too hot to run a trans. Again, a true linear gauge gives you some warning that something is about to go wrong, rather than telling you that something just went wrong.
 

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jdholder said:
I will absolutely allow the cars existing sensors/electronic/warnings do the job as per the design of the car. However, I would rather have more granular information to warn me in advance that I am about to get a "trans overheat" warning.

Since I don't own a testbook or blackbox, and I regularly go 50 to 100 miles offroad, away from civilization, I feel like more information is better. So, if I see the trans temp start to creep up while I am crawling along in deep sand, I can stop and cool the trans before the dreaded "BONG" that makes my stomach drop each time I hear it.

Also, from my race car experience, I have found that often times the "factory warnings" occur just at the point of major problems. For example, it is common for the S54 motor in an E46 BMW M3 to run an oil temp of 300 degrees. No warning bells go off while running around at 300 degrees. However, I don't want my race motors running 300 degree oil temps, so I rely on a programmable dash where I can set the warning temps to my desire. As a final example, the Ford Superduty has a trans temp gauge as factory equipment, but it is a well documented fact that the neddle on the gauge stays in the "normal" zone with tranny temps from 100 to 235 degrees. It only starts to move toward the hot zone at 240 degrees and by the time the needle is in the red, the trans temp is 255 degrees. It's a common belief that 255 degrees is too hot to run a trans. Again, a true linear gauge gives you some warning that something is about to go wrong, rather than telling you that something just went wrong.
Wow that told me :clap:

Excelent and very informative answer, I had no idea you did such extensive off-roading and am in awe of you going 100 miles in the back country.

Get that temp gauage fitted ASAP :lol:
 

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Discussion Starter #10
Ok -

Got the installation of Trans Temp and Oil Temp completed and just in time.

It's 85 degrees here in SoCal today, and I did a drive to see what the baselines are - I'm a little worried.

Bottom line, trans temps were "normal" at 210 degrees. We drilled and tapped the pan (after removing it) to place the sender there. I did some spirited driving and was able to get the trans temp up to 225 degrees. I feel like this is too hot - and I can't imagine what it will get to when crawling slowly through deep sand in 100 degree desert heat. I think I am going to address this with an auxiliary trans cooler. If this is how hot they normally run, no wonder they wear out at 85k to 125k miles.

Engine Oil Temps hovered around 240 degrees. Perhaps an Engine OIl Cooler is also necessary - thoughts?

See pic!

 

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Because the transmission uses an oil-water rather than an oil-air cooler you would expect the transmission fluid bulk oil temperature to average around 195 - 210 deg. F.

The overheat message from the ECU won't be triggered until a fluid temperature over 255 deg. F is detected, which will be off your gauge.

If you can get access to the large multiplug at the back of the transmission you could check the gauge calibration against the transmission's built-in sensor (pins 13 &14)?

Phil
 

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I just found this thread which is extremely helpful as my message centre is displaying the transoverheat message and the temps per my laser thermometer are around 180 F and the water temp is 140 to 160 in and out with oil temp about 10 degrees cooler on the other side of the trans cooler. So my thought is that I really need to replace the trans wiring harness and perhaps because I likely had true overheat conditions about 1 and a half years ago when the cooler was totally plugged (since replaced). I have not yet done a resistance check as per Phil's notes and graph displayed on another post. Just wanted to say thanks since I was unsure of what the trans temps should be and what might trigger the message and this blog has helped me immensely:-D
 
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