Trans temp from 163 degrees and up. No codes.when coming to a stop trans doesn't always shift down into low gear. Raise RPM to 1500 slams into gear. Trans service and flush completed 3 months ago. What could be causing this?

 

this could be the problem. how many miles on the trans and did you have any issues before the flush.
the reason the flush could be the issues is even GM say NOT to do one for any reason and the only reason to use the flush machine is on transmission coolers after a bad trans was pulled as it will cause a trans to fail

 

Was the trans service completed because of the problems you were experiencing or did the problems start after?

The 2010 Silverado manual says to change the transmission fluid every 50,000 miles. I'm assuming by flush that means replacing the filter then allowing the pump to push out the old fluid while adding new fluid until the fluid runs clear. This would cause no issues with a properly functioning transmission.

Are any codes stored in the TCM? You may have a bad solenoid or valve issue.