2012 suburban vs 2014 sierra transmission temps

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jstutz

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Hey guys, I recently bought a 12 suburban and took a trip with my family which owns a GMC Sierra truck. Just for fun we monitored different things on the way to the beach and found a few things different. His transmission temp rises way faster than mine and stabilizes as 194 F. Mine stabilizes at 149F on highway and around town it got as high as 180F. His did not seem to change much during the different conditions where mine was all over the place. He also got about 3 mpg better than I did on avg based on the truck calculator.

Does anyone know why the trans temps are different? Maybe his is plumed thru the coolant and mine is not. Not sure.
 
Originally Posted By: jstutz
Hey guys, I recently bought a 12 suburban and took a trip with my family which owns a GMC Sierra truck. Just for fun we monitored different things on the way to the beach and found a few things different. His transmission temp rises way faster than mine and stabilizes as 194 F. Mine stabilizes at 149F on highway and around town it got as high as 180F. His did not seem to change much during the different conditions where mine was all over the place. He also got about 3 mpg better than I did on avg based on the truck calculator.

Does anyone know why the trans temps are different? Maybe his is plumed thru the coolant and mine is not. Not sure.


Both have a Trailer Package?
 
The average rule of thumb for transmission temps are 100 degrees over ambient temperature-in GM half ton trucks with the six speed transmissions.


This is discussed to death on the various truck forums on the Internet.


BTW-the Dex 6 has been tested up to 275 degrees.
 
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I think trans has a thermostat in it. Until the temp reaches set point the cooler is bypassed. Look it up, there is an easy way to "Rig" the valve to limit the bypass.
 
Transmission fluid cooler and transmission fluid heat exchanger can have an impact.

Cooler (most cars with towing package may have it) helps in keeping the trans temp cooler like a radiator for coolant.

Heat exchanger (I don't know if all trucks have it not) will also help to cool off the trans fluid when the trans fluid temp gets above your coolant temps. It also help to warm up the trans fluid faster when it's cold (or in winter when the car has been sitting over night).
With heat exchanger the trans fluid is piped thru coolant and as the engine warms up and coolant temp rises, it will heat the trans fluid.I

If you have heat exchanger you will see (in general) more steady trans temp right around the coolant temp +/- and without it you will see a wider swing. Lower temps when car is cold and maybe much higher temps (relative to your coolant) if towing in summer. Basically if you have heat exchanger coolant can cool off your trans temp if your trans temp goes higher than coolant ...

You need to find out which car has what ...
 
Forgot to mention that if you don't have heat exchanger, you will see (again in general) lower trans temp under normal usage (e.g. not towing) than the same car that has the heat exchanger. Because heat exchanger under these conditions is putting some heat into your trans fluid. But it has benefits when too cold or too hot to stabilize the trans temp to about your coolant temp.
obviously there are pros and cons beyond the scope of your question ...
 
Originally Posted By: OilUzer
Forgot to mention that if you don't have heat exchanger, you will see (again in general) lower trans temp under normal usage (e.g. not towing) than the same car that has the heat exchanger. Because heat exchanger under these conditions is putting some heat into your trans fluid. But it has benefits when too cold or too hot to stabilize the trans temp to about your coolant temp.
obviously there are pros and cons beyond the scope of your question ...


GM will have a unit in coolant … with trailer package should also have a stacked plate cooler in front of radiator …
 
Also regarding better (3 mpg) fuel economy, assuming that everything else is the same (i.e comparing exact same trucks), if the transmission fluid is at a more optimal temperature/viscosity range (using heat exchanger), it will help the fuel economy. I don't know if it impacts that much (3 mpg) or not but it does help.
Again there are pros and cons ... Some say better fuel economy vs. running hot(er) which may not be good for the transmission...
People argue over that like they argue over thin vs. thick oil ... lol

this is besides the point but fyi,
I know people with trans cooler who have removed their heat exchanger which is imho ok if you are living in mild climates. In regions with very cold winter or colder in general, the heat exchanger helps to warm up the trans fluid which is a big plus.
Best is not to mess with it trying to outsmart the engineers unless you really know what you are doing. Engineers have to design for all conditions (one size fits all) and there is always room to mess with things.
wink.gif
 
Thank you guys. I figured being that they were so different that there must be a design difference. I can see how this would be a good thing in the colder temps. This morning, on my way to work, my trans temp never got above 130F. Having the transmission fluid temp more stable seems like a good idea. I would think that todays synthetic ATF's should handle 195F pretty well.
.
 
Originally Posted By: clinebarger
Starting in 2014.....GM used a Thermal Bypass Valve on the 6L80E, Your 2012 6L80E doesn't have one.


Clinebarger … I have 3 GM automatics … if I’m sitting at a long multiple lane traffic light … I have always popped the transmission in N rather than hold the brake against the TC …
Is that better for the transmission or ATF ?
 
Originally Posted By: 4WD
Originally Posted By: clinebarger
Starting in 2014.....GM used a Thermal Bypass Valve on the 6L80E, Your 2012 6L80E doesn't have one.


Clinebarger … I have 3 GM automatics … if I’m sitting at a long multiple lane traffic light … I have always popped the transmission in N rather than hold the brake against the TC …
Is that better for the transmission or ATF ?


I highly doubt it helps anything. Your unloading the Turbine & to a lesser extent the Stator which in theory would help reduce heat. But at low idle in gear not much "fluid coupling" is happening. The act of fluid coupling is what creates the most heat.


On 4L60E's & it's derivatives......Cycling the Forward Clutch more than necessary can result in stripped clutch plate drive splines &/or accelerated friction wear. The Forward Clutch was not designed to be Dynamic....It was designed to be Static most of the time.

GM did update the Forward frictions in 2003 by adding grooves to the friction face, This did help with friction material wear, But did nothing for drive spline wear....If anything this made it worse.

On 6 speed auto's.....Just about every clutch pack is designed to be Dynamic as they don't have dedicated forward clutch.
 
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