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 4L60E - Too hot!

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jayoldschool

jayoldschool

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeFri Apr 03, 2015 7:47 pm

Converter not locking?
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeFri Apr 03, 2015 8:02 pm

The PCM is going into hot mode, which prevents O/D deliberately, because the engine temperature is rising. In other words, your problem is not the transmission but the engine.

Most likely issues: a plugged radiator core, missing thermostat (the LT1 thermostat is different from a traditional T-stat, and will cause overheating if removed), or cooling fan failure. The tow-pack car should have a mechanical fan (which relies on the clutch) and an auxilliary electric fan on the driver's side of the rad. It should be obvious if the electric fan has failed -- is it running when the car is hot? The mechanical fan should not spin more than a couple of turns when spun by hand with the engine warm but off.
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeSat Apr 04, 2015 6:26 am

The gauge ECT sensor is in a different location than the PCM ECT sensor. Since there are two, a good quick check is to see if they roughly agree with each other. You can do this using a scan tool or through the CC display. The gauge is not very precise, but it's about 10°F per tick mark, IIRC. 180°F is at the 1/2 way mark (again, IIRC). Compare that to the scan tool value. In the CC display, -08 is reputedly the ECT in °F) Or use a handheld thermometer to measure the temperature at the thermostat housing (a laser type is great for this).

The transmission temperature gauge sender is in the line at the transmission. If your aftermarket gauge is plugged into the diagnostic port, then it's probably using that sensor. If it has it's own sensor then you'll have to follow the wires. But it's possible that the transmission temperature display is wrong. Try measuring the temperature of the transmission line itself (with a handheld thermometer of some sort) and compare to the gauge reading.
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeMon Apr 06, 2015 6:53 pm

According to the GM Factory Service Manual, the normal transmission operating temperature range at idle is 30° to 130° C. That would be 84° to 264° F.

So assuming you are talking in Fahrenheit, then the tranny shop is correct and you have nothing to worry about (at least, as far as temperatures go).
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YachtDriver

YachtDriver

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeMon Apr 06, 2015 11:47 pm


My SSWAGON has a VDO transmission temperature gauge. It typically hovers around 175. In traffic it can get up to 200 or so. This is at the test port.

Summit page with the temperature gauge.
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeTue Apr 07, 2015 9:13 am

I think that chart is probably specific to a particular fluid, but I think the general principle is valid -- transmission fluid life is inversely proportional to temperature. Clearly cooler is better.

Here's an authoratative-sounding tidbit provided by Google. Not specific to these cars, but the Silverado uses the same 4L60E transmission:

Quote :
In the February 2011 issue of Trailer Life magazine RV Clinic in response to a reader about the maximum transmission temperature allowed in a 2009 Chevy Silverado, the Tech Team had this response.

“General Motors’ in-house towing team expert provided RV Clinic with this statement: The maximum allowable automatic transmission fluid temperature is dictated by the transmission oil itself. The oil begins to degrade significantly above 270 degrees Fahrenheit, so we design vehicles so that in all but the most extreme conditions, the fluid temperature in the transmission sump stays below 270 degrees F.

We allow for up to 285 degrees F in extreme conditions (i.e. towing a trailer with combination loaded at GCWR in Death Valley). But for customer usage anywhere else in the country, even at GCWR, transmission sump temperature should stay well below 270 degrees F. Above this point, certain internal components, such as seals, begin to disintegrate rather quickly. Although newer synthetic fluids can withstand higher temperatures we still recommend this (270F) as a maximum temperature. "
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sherlock9c1



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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeTue Apr 07, 2015 5:40 pm

I posted over on the ISSF but got drowned out by the experts over there, so so much for that.

As buickwagon said, transmission temperature is driven mainly by the ATF you use.  Dexron 3 was not all that good at a number of things including handling high temps, but it's relatively cheap.   Dexron 6 is lightyears better particularly in terms of constant viscosity over temperature and long-term durability at higher temperatures.   The clutchpacks have to get REALLY hot before they start to overheat and deform, and that's almost solely due to excessive slippage under really big torque loads.  In other words, if the trans is just "hot" (like over 220F) and the shifts aren't sloppy, you won't damage the clutchpacks.

BTW, the fact that the shop actually did diagnostics and didn't just say "needs rebuilt" is HUGE.   I'd keep that shop in mind for future work.
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeThu Apr 09, 2015 3:13 pm

For fun I took the Tech2 on a recent trip and monitored my transmission temps.

Car was essentially empty. Ambient temps were around freezing or a few degrees above. There was intermittent rain and freezing rain most of the trip. Highway cruising was mostly gentle hills with the cruise set to ~100 - 105 kph (60-65 mph). City driving was with a gentle foot on the throttle and brake. The transmission was just rebuilt this past winter (and adaptive shift tables, PC solenoid pulse width, etc. show it's right on spec). Gear selector was in OD for the entire trip.

On cold start, the transmission temperature climbed to 39°C by the time the engine was up to full operating temperature. It then slowly climbed up to around 47°C (117°F) (fluctuating +/-1°C for the next 2 hours.

On entering city traffic, temps soared to more than 70°C (158°F) within about 10 blocks, but stabilized there.

On returning to the highway for the trip home, the temperature slowly dropped to the 47°C seen earlier. I tried a few "pull out and pass" simulations and the temperature would remain about the same, then climb 1 or 2° shortly after or while coasting down, then return to 47°C.

On stopping for fuel, I noticed the temperature climb to 65° just sitting there idling. Again, it slowly returned to 47°C once I got back on the highway.

The trip terminated in a 5km leg of winding, hilly, rural road and the temperature hit 68°C (155°F).

One thought that crossed my mind during this trip: If a brake was dragging, transmission temperatures would probably rise.
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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeThu Apr 09, 2015 3:40 pm

Learned a lot from this post so far and now know that a trans temp gauge will be going into the third spot of my pillar pod.
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bamalongroof

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeThu Apr 09, 2015 11:18 pm

Dan,
Silly question I know.... but do you have a known true gauge? jeff
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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeFri Apr 10, 2015 10:41 am

atlantadan wrote:
bamalongroof wrote:
Dan,
Silly question I know.... but do you have a known true gauge? jeff
Excellent question, actually. I've used a laser IR thermometer on the pan, and the temps are very close to what the gauge is showing.

Been using one of the early laser IR thermometers for years,amazing tool for automotive and home use.I use a fluke model now and love it!
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sherlock9c1



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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeFri Apr 10, 2015 10:04 pm

My own experience with a cyberdyne digital trans gauge & sender in the pressure test port was that trans temps tended to stay 60-90F higher than ambient while moving. When stopped, they would tend up to engine coolant temp (220F) and stay there. I think the hottest I've ever seen was 235 while garage-saling on a summer day; as soon as I got above 35mph, the temps went right down to the range I listed above.
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phantom 309

phantom 309

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeSun Apr 19, 2015 8:53 am

perhaps just do an 4L80E swap,..
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeTue Apr 21, 2015 8:12 pm

It may be the sensor, the internal harness or the external harness, or normal operation if the car was started with the fluid temperature below -40° for 1 second or more. (High voltage = high sensor circuit resistance = LOW fluid temperature reading). It could even have been set when one of the transmission shops disconnected the harness for some tests, if they did not clear the codes again afterwards.

I personally would do a little more investigation before replacing the internal harness.

A broken wire or poor connection anywhere in the system (inside or outside the transmission) can cause this code. There is a series of checks in the manual that will progressively and logically isolate the problem. However, it takes a while and might miss an intermittent fault. Use your scan tool to read the current fluid temp reading, if it's correct and you have never started the car in extreme cold weather, then get an assistant to watch the value on the scan tool while you wiggle the wires between the transmission and the car.

If you can't find an intermittent, then try clearing the code and see if it comes back.

If the problem is consistent, there's a chart in the FSM (p. 7A-14A-Cool that shows the temperature/resistance relationship. For example, @ 70°C, the resistance should be between 420 and 514 ohms. At 100°C, the resistance drops to 119-150 ohms. Measure the resistance at the harness connector transmission side between pins L and M. Is it infinite, just high, or consistent with the current actual fluid temperature? Jumper those same two pins on the car side with a test light or fixed resistor and check the scan tool temperature value against the resistance you applied.

These tests should at least confirm if the problem exists inside or outside the transmission. If it's inside, then you have to open it up to tell for sure, but if the internal resistance is infinite, then it could be the sensor itself, the connector or the internal harness. If the internal resistance is just high, then my money would be on the sensor itself.


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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeThu May 07, 2015 11:57 am

atlantadan wrote:
Another question - So, the trans temp gauge isn't hooked to any sensor on the trans line, nor is it in the pan, nor is it in the test port on the side. The wires go into the harness and then, I THINK, they terminate at the PCM. This raises a weird question - where the hell is the gauge getting the temp data from?!?? If the temp sensor in the trans is faulting out, its not getting it from there, so it must be getting the data from the sensor in the brass-block in the line, correct?

If so, that's an entirely new way to hook up that gauge. How accurate do you think that temp readout actually is?

Since this is an aftermarket gauge, and since I can't even see it, then your guess is as good as mine. There is no reason as gauge could not be monitoring the PCM sensor -- either at the sensor wires to the PCM or via the PCM through the diagnostic data serial output line. If the former, the tap would have to be carefully calibrated to avoid skewing the reading of course. If the latter, there would have to be some sort of serial interface to read only the transmission temp output and to convert the digital results into an analog gauge output (seems a waste of processing power) but it could be done as far as I know.

As for the accuracy, well, a chain is only as strong as the weakest link. Is the sensor in spec? Is the wiring tap parasitic? Is there corrosion in a connector somewhere. Is the conversion algorithm correct? Is the gauge itself accurate? There's a lot of places where something could go wrong.
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buickwagon

buickwagon

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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeSun May 10, 2015 12:20 pm

So the wiring tap was parasitic -- parallel resistances preventing either the PCM or the aftermarket gauge from getting an accurate reading due to the presence of the other device on the line.

So what are the actual temperatures? Inquiring minds want to know.
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sherlock9c1



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PostSubject: Re: 4L60E - Too hot!   4L60E - Too hot! Icon_minitimeMon May 11, 2015 11:47 pm

After years of running a trans temp gauge on my 9C1, it always ran 60-90F hotter than ambient. Other than that I quickly found that the gauge was useless, but now I had a hole in my bezel so I just left it there.
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