Transmission runs at 230-235F after about 15 min or so of driving. Where should I start?

​​Transmission fluid and filter been replaced about 8K miles ago, level and color looks fine. I did get an external cooler but haven't installed it yet. Wanted to see if 230-235F is a sign of a problem that needs to be addressed, or if thats typical/normal with 125k miles.

 

The average temperature will be between 175 to 220 degrees.
However, the transmission temperature can go as high as 240 degrees Fahrenheit if pushed to its limit.
This straight from Google search.

Might wanna start doing some checks. Radiator, water pump, thermostat,etc...
What's your air temp where your at?

 

It's 100-110F outside. Everything in the engine cooling system has been replaced, and I mean everything.

 

Okay.
I'm not surprised that the high temperature is occurring. 100+ degrees.
Might be time to do a stand alone transmission cooler.

 

Is your temp. gauge accurate?

 

Got a standalone cooler in route. Do you drain your ATF when installing one of those? All the write ups I see don't mention that. Not sure how much fluid I should expect to come out of the lines once I disconnect them from the radiator.

good question, I am using torque pro and a OBD dongle to monitor.

 

6-8 ounces or so, its only about 2 loops. Just top off what was lost. I always have some rubber vacuum caps on hand to temporarily cap the lines until ready for a reconnect, and use foam ear plugs in the Radiator quick connects for temporary plugs there.

 

The normal(optimal performance) operating range for a 4L60-E is between 160° and 180°!

Transmission temperature you can expect the transmission to last:

 

Good to know, thanks Doc!
I'll have everything up and routed before I disconnect and flare the lines. The only other thing I am wondering is whether or not I should get a thermal bypass, we do get some cold days during the winter time, but nothing to extreme. This past winter we actually got some snow, but that's a rare occurrence.

Ooof, I saw this chart on a different cooler I got for my chicken coop. A bit unsettling considering I have no idea how long this truck been running with transmission temps around 230F. I am also not sure just how accurate my scanner is. Could I send a temperature probe down the fill hole to check?

 

Did you check transmission cooler lines temp with IR(pointed at steel, not rubber)? Did you pull the dipstick, wipe on a white paper towel, and check color & smell?