Driving around this weekend in 90 degree weather, the transmission all of the sudden decides to shift super hard, after getting off the freeway and putting around on side streets. Every gear shift super hard, of course 1 to 2 being the most noticeable. No matter the speed I was going, it was shifting hard. Turned the car off for 10 minutes and started driving again, all back to normal. Hasn't done it since... Any ideas why it would do that ?

 

Scan for codes. A code related to slipping will cause the PCM to command max line pressure which makes the shifts very firm.