Install a transmission oil cooler and remove your shroud and clutch fan. And install a high CFM electric puller fan.
Easier said than done. Removing the trans cooler has little effect on ECT (engine coolant temps). Its actually the other way, ECT will be driving the trans temps up or down. Now when you mount the trans cooler externally, the trans temps are no longer driven by ECT and this lets trans temps to hover lower. Offcourse that also means it will take longer to heat it up.
As for the ECT, the radiator will get less airflow which is also hot air from the trans cooler, reducing radiator efficiency and cooling.
If the OP wants to have better cooling, the T-stat (if it was changed) is a reason. The oem stat was lower but sometime in 2009 GM decided to use a higher rated T-stat to improve emmisions (as a result higher needle amd ECT). I have an 06 and it runs the same temps as thr OP after my T-stat change.
Finally, the clutch fan pulls alot of air. You need serious efans to make up for it and thats $.
You are looking at 500+
I recommend a flush, make sure nothing is blocking the condenser, check T-stat and finally, invest in a proper 16" pusher fan. Something that pull big amps. CFM ratings are junk if they dont show what restrictions they are rated for.
