Anyone out there have an idea what the normal healthy temp range is for the transmission? My Tahoe is constantly in the 170 - 180 range and it has the external cooler? Its a 5.3 LT 2wd, 07. I searched the forum and it seems this normal and maybe even good considering the mileage(118K) on my Tahoe??

 

Sounds normal for no-load in the summer time.

 

I would concur that that sounds normal but what is the outside temp?

I just added the factory cooler a couple of months back and that is about the range I get with the outside temp in the low 90's... its been in the 150-170 range with the highs now only reaching into the mid to low 80's

 

ours will get that high on the highway in the summer but it takes a while. now with temps in the 70s or 80s it will stay around 160 - 170 after an hour of driving.
it really depends on outside temp and if you are stop and go or all highway.
ours got close to 200 when we were in stop and go behind a wreck for 30 minutes then cooled down to 170ish once we got going.

no tranny cooler 2wd fyi

 

we were getting into the 220s when towing our camper trailer, if you do any towing I would recommend the factory trans cooler form GM parts direct, its was easy enough to install, a little bit of a pain in the **** but do-able and worth it...

 

Your tranny temp will be the same as the engine coolant temp.
The engine warms the tranny.
If there is a tranny problem or it is working hard in high ambient temps the tranny will add heat to your engine coolant.

 

Mine always runs lower than the coolant w/ or w/o an external cooler unless it's a really hot day.