Remanufactured Transmission Temp

[swathdiver]

The temperature gauge on the dash is intentionally slow and imprecise so as not to alarm the low information drivers; it keeps them from clogging up the service departments. For some reason, they had no such reservations about the accuracy of the voltage gauge!

 

[B-train]

While in overdrive at a steady speed, lightly push the brake pedal with your left foot(basically enough to engage the light switch) . With your right foot still holding steady speed, watch the tach and see if it jumps up (usually a couple hundred rpm). It should stay up while stop switch is activated. Once you let the left foot go, you should see the tach go back down in rpm if the torque converter is locking in correctly.

Tow haul mode will lock up the torque converter sooner. I think it engages after 2nd gear if memory serves right.

 

[jabre]

I appreciate the inputs to my issue. This has been a learning experience. It is very infrequent for me to take long (>30min) drives in this vehicle. So, it has taken some time to learn more about my perceived issue. I did actually buy a Raspberry PI, dual ADC and temp probes. But, ended up not geting around to even using them since I was able to monitor to get the info I (believe) needed. Observations in no particular order.
- Bluetooth OBD reader + Torque are an indispensable toolset. Now that I am set up with the tools and an old tablet in the vehicle to monitor and log I have learned a great deal.
- I do not have a supplemental (external) transmission fluid cooler.
- Since I don't have the external cooler my 'cooling' is limited by the radiator heat exchanger which is a cylinder immersed in the coolant. As such, it cannot 'cool' beyond the capacity to heat exchange with that coolant.
- I've monitored my engine temp with Torque. My conclusion is the dash gauge is worse than useless - it is just plain erroneous and misleading.
- On my latest long drive around town with some highway driving I monitored the coolant temperature.
---- In town, warm weather stop and go, it goes beyond the 190 thermostat temp. I watch it rise up to the ~220 deg high speed radiator fan temp and can hear that fan kick in.
---- Once on the highway the coolant temperature tracks down towards the 190 with the additional air flow.

- The transmission temp slowly rises over quite some time. My guess is that there is an internal thermal valve for the fuid flow as it takes much longer to warm up than the engine temperature.
- I can verify the Torque converter lockup by monitoring the transmission slip. It is locking.
- When in stop and go traffic the tranny temp will rise as high as about 8 degrees above the engine temp.
- When moving with good air flow and higher RPMs I can see the transmission temp track down from the higher temps with the engine temperature.

IMHO:
- Without an external transmission cooler don't expect the transmission temp to be below the engine temperature after it warms up.
- 'Normal' transmission operating temperature is the engine (coolant) temperature.

 

[Geotrash]

You’re doing great investigating! Great to see it.

I’ll add to the other good advice here and just say that the slow rise of the transmission temperature you’re seeing is about right. When the fluid is cooler than the coolant in the radiator, the radiator warms it up. And the opposite is true when it’s warmer than the coolant. Dexron VI is stable to 265°F, same as your coolant.

That said, if you’re ever going to do any significant towing, I would consider an external cooler plumbed in *after* the radiator’s fluid cooler and before the fluid returns to the transmission. Lots of people have the Trucool 40k but in my opinion that’s too much cooler. I have one in my ‘07 and can’t get the fluid to the 150°F that GM recommends, even on long drives in traffic. I have a Derale 13960 in my ‘12 and that’s a much better match.

 

[Foggy]

IMHO:
- Without an external transmission cooler don't expect the transmission temp to be below the engine temperature after it warms up.
- 'Normal' transmission operating temperature is the engine (coolant) temperature.

From Jabre's Post:

I see his points, but have to disagree with some of the conclusions..
Trans temp will generally be BELOW coolant temp when your ambient temps
are not "summer" temps. See what happens when weather cools.
When your trans torque converter clutch is engaged and your are "locked up" the
trans will actually act as a heat sink for the engine coolant.

Normal Operating temps are going to be controlled by your airflow, ambient temps,
and your radiator/fan capabilities..

I've driven quite a few "stock" gmc/chevy trucks with the 6L80E/ 4l60E/ 4L80E,
they all behave the same ish..
Trans temps will rise very quickly under heavy load/accel and then drop back
down very quickly when you are at a steady state

Also, some ECM's, temp gauges and sensors are located in diff positions.
I have monitored my trans temps according the trans computer(stock&standalone systems)
and can compare those with actual PAN Temps with a temp sending unit in the pan itself.
That is really what is important - the pan temps- as this is the fluid that being sucked
up by the filter and going INTO the trans itself to be used.

As others have pointed out, the newer synthetic fluids are good up to
higher temps and the trans components themselves are built for higher temps too.

If I missed something in the post, sorry... Maybe your actual radiator is in need of
some TLC or replacement if your trans temps are too high. You are correct in assuming
the trans temps without an aux cooler are controlled by your coolant temps (not always though).

 

[jabre]

@Foggy,

I have a new AC Delco radiator. Factory fan that seems to be operating properly with no flow restrictions. I am in Texas. The current local weather may still be considered 'summer' by many on this forum

I'll definitely re-log the temps once we get some solid weather changes in the area. I would not argue against any of your points. But, importantly for me, I don't think anything I am seeing with the operating temperatures of this transmission indicate any problems. The only thing I would change now is to swap out that *&@#! dash temperature gauge for something that is more accurate. It aggravates me every time I look at it now.

 

[Foggy]

@Foggy,

I have a new AC Delco radiator. Factory fan that seems to be operating properly with no flow restrictions. I am in Texas. The current local weather may still be considered 'summer' by many on this forum

I'll definitely re-log the temps once we get some solid weather changes in the area. I would not argue against any of your points. But, importantly for me, I don't think anything I am seeing with the operating temperatures of this transmission indicate any problems. The only thing I would change now is to swap out that *&@#! dash temperature gauge for something that is more accurate. It aggravates me every time I look at it now.

I have always hated the coolant temp "dummy gauge" too... 180*-220* is all the same
at the middle 210*.. There is a water port open on the passenger side head.. It's at the back
so depending on how you want to tap into it !!! opposite of the oe temp sender on driver side
front head....
I just don't know where I'd mount an autometer temp gauge as I already have
my wideband O2 gauge and vacuum/boost gauge
I'll prob just throw my diablosport trinity back on the dash to monitor things
(I'm tuned with my HPTuners)