Transmission fluid temp.

[puma]

So I put a Auto Meter trans. temp. gauge into my '05 Sierra crew 4x4 with 5.3L, 4L60E and 3.42's with the sensor installed into the return line from the coolers. I was told by several people that this is a good spot since it measure close to what the pan temp will basically be and what the trans. is running at.

So normally it will sit at somewhere between 110°F and 130°F during normal driving in 75°F to 80°F

I put a good test on it this past weekend with our 29ft. travel trailer attached (5600 lbs.) and the truck fully loaded driving 100 miles at 100 kph (63 mph), 33°C (92°F) outside, 80% RH and a headwind which makes the truck work hard. Hard enough that it stays out of OD.

I still only saw fluid temps. of less than 155°F and during stop and go driving in the city that same day with the trailer it still stayed well below 175°F.

Is this normal? It seems somewhat low for what I expected to see in these conditions. My old '92 GMC with the same trans. pulling the same load in the same conditions would sometimes have a pan temp. of 200°F.

P.S. I'll post pics of the gauge, pillar pod, sending unit and wiring shortly. It's amazing how hard it is to find a wiring diagram for a vehicle when you want to know which colour wire for dimming the panel lights, etc.

[kcb37]

That's a good thing.
If it hits 200 say going up a hill and goes back down once you crest then your still fine. However you seem to be setup well. Keep driving like you are so as to not heat it up more, and your trans should keep together along with the fluid making it farther.

[someotherguy]

I strongly disagree that it should be in the return line from the cooler. You're measuring the fluid AFTER cooling, not before, so you have no idea what the actual temperature of the fluid got up to which is what you really should be watching for.

People will argue this one forever but I use the pressure test port on the side of the transmission case. In hot weather (90's and so fahrenheit) I see around 170F-180F unloaded, a little more when working it. I've confirmed these temperatures by shooting all over the case and pan of the transmission looking for the maximum high reading I can find (the infrared thermometer I use has a "max" reading function so it's really easy) and the gauge has been very accurate installed this way.

Richard

[puma]

I strongly disagree that it should be in the return line from the cooler. You're measuring the fluid AFTER cooling, not before, so you have no idea what the actual temperature of the fluid got up to which is what you really should be watching for.

People will argue this one forever but I use the pressure test port on the side of the transmission case. In hot weather (90's and so fahrenheit) I see around 170F-180F unloaded, a little more when working it. I've confirmed these temperatures by shooting all over the case and pan of the transmission looking for the maximum high reading I can find (the infrared thermometer I use has a "max" reading function so it's really easy) and the gauge has been very accurate installed this way.

Richard

I was told that if you measured the temp. leaving the torque converter to the coolers then you would get scared when you saw the fluid hit 275°F going up a grade or holding a stall up a grade. They say that since this is not the actual temperature that the transmission is running at and doesn't stay at this temperature continually, you are better to measure the pan temperature which is an average temperature.

Since the pan is inconvenient to put a sensor in then the consensus seems to be the return line from the coolers which they say is the next best thing. The pressure test port is also considered a good place but lots of people find it either inconvenient or are not comfortable putting it there.

This is what I am generally being told.

[someotherguy]

I've never seen a crazy spike like that in my temp readings, and one of the applications I used the pressure test port was on the 4L80E in a 1996 C3500 dually with a wrecker unit on it, while pulling uphill (mind you just a long freeway flyover ramp approach) with 4,000lbs+ on the back, maybe saw 210F?

The pressure test port is dead easy to access on 700R4 / 4L60 / 4L60E / 4L80E, dunno why anybody would say it's inconvenient. The sender that Autometer includes with their gauge screws right in with no adapters needed, then you attach the single wire to it and run to your gauge (and of course key-on +12 and lamp power to the gauge itself) and you're done. Couldn't be easier.

The sender used in the test port is NPT (national pipe taper) so it essentially seals itself as you snug it down; incredibly unlikely it could ever leak, unlike one installed inline with a cooling line which is now a potential spot the lines could separate. Believe me, when you pop loose a cooling line while running you will lose the fluid so fast your transmission will be destroyed before you can even think to pull over and shut it down. Has happened to a couple people that I know...

Richard

[XLR8N]

Hot temps will cook your trans before the fluid is cooled. Not sure why someone would tell you to have it installed after?

[boogie_4wheel]

I use the pressure test port on the side of the transmission case.

I agree!

I was told that if you measured the temp. leaving the torque converter to the coolers then you would get scared when you saw the fluid hit 275°F going up a grade or holding a stall up a grade. They say that since this is not the actual temperature that the transmission is running at and doesn't stay at this temperature continually, you are better to measure the pan temperature which is an average temperature.

Since the pan is inconvenient to put a sensor in then the consensus seems to be the return line from the coolers which they say is the next best thing. The pressure test port is also considered a good place but lots of people find it either inconvenient or are not comfortable putting it there.

This is what I am generally being told.

I don't see how the test port is inconvenient; remove plug from side of trans, and thread in sensor, done. Easily half the time of the cooler lines (exiting or returning) and your going to get a more accurate reading.

The return line from the cooler doesn't matter; We don't care how good a fluid cooler you have, we care about internal temperature. Think of it like this, where is the coolant temp sensor on the engine located? Not on the lower radiator hose, it is on the head or near the thermostat. You could have a plugged/pinched cooling line and show a nice cool trans all the while the poor little bastard is glowing underneath the truck.

Factory installed sensors are not in the cooler lines, they are inside the trans, and the closest that your going to get to them is by using the test port.

[someotherguy]

Yet at least half the people discussing the subject will argue that the pressure test port isn't a good place for the temp sensor. HMMM, it's a good enough spot to do pressure testing to determine if the transmission is operating correctly; I think it's got a good supply of fluid to determine the temperature, too.

Richard

[DylanC]

Anyone know of a good temp meter i wouldnt mind hooking up one my self this weekend

[boogie_4wheel]

I'm runnin an Autometer Sport Comp electric with a black face (I tried to get something that looked close to the factory gauges) then mounted it in a single gauge pod on the A-pillar.

Wiring is simple. Tap a wire for a keyed source, ground, tap the instrument panel fuse for illumination and every vehicle I've done this to will dim with the rest of the gauges on the fuse, and signal wire.

[someotherguy]

Autometer Z series is pretty close to factory gauges too; black face, white sans-serif letters, orange (well, red-orange) needle. Using the included green cover for the bulb is similar to the green glow in the factory gauges.

On 1988-1994 it's real easy to tap "key on" 12V power; the terminals marked WHT on the panel under the dash:



The yellow wire with the crimp terminal is feeding 12V to my trans temp gauge...and here's where I put it:



The needles match a little better since I put a cluster in that doesn't have such faded needles.

Richard

[XLR8N]

The guy sitting on your dash looks like he can be a real prick.

[someotherguy]

The guy sitting on your dash looks like he can be a real prick.

He's just keeping an eye on me, making sure I'm doing it right.

Richard

[puma]

So by the replies I assume then that I have wasted my time installing a trans. temp. gauge that measures the fluid temperature returning to the transmission.

What everyone is saying makes complete sense but it seemed to me that after a fair bit of research that people were divided about sensing in the pan, sensing in the pressure port or sensing in the cooler lines.

Who would of thought. I went with the simplest for me at the time especially since I needed it the next day.

Another confusing issue is that I'm told the fluid leaves the trans., goes into the aux. cooler, then to the rad cooler and then back to the trans. I would of thought that the last place the fluid should go is the aux. cooler rather than get reheated by the rad cooler

I was told this is to prevent over-cooling.

[speedracer326]

You need to ignore whoever's giving you such crap advice. It hits the rad cooler first, then the aux cooler. If GM gave that much of a crap about overcooling, they could have simply installed a thermostatic bypass to the aux cooler.

[seth350]

I have a stock trans gauge and it will always read over 200, no matter the ambient temp. I saw it get real high while driving in the smokey mountains in the winter, wasnt red line but it was close. I had the trans fluid flushed (I told them to just change it, but the service center flushed it regardless). Still reads around 200 or 210. Just telling you for comparison.

[CKTA]

Another confusing issue is that I'm told the fluid leaves the trans., goes into the aux. cooler, then to the rad cooler and then back to the trans. I would of thought that the last place the fluid should go is the aux. cooler rather than get reheated by the rad cooler

I was told this is to prevent over-cooling.

That is true. It sound wierd, but it's true. I know this because I installed a GM cooler kit and that's how they told you to hook it up.

I have my B&M Supercooler installed the other way on my other truck because that's the way they wanted it because their cooler has a bypass of some sort in it.

[kemble]

My SS cluster transfer gauge read 200 most of the time with the factory auxiliary cooler. Now with my 2 times as big aftermarket auxiliary. Cooler it reads 150-200 depending on temp and useage.