2001 2500HD hard shifting

Hi, I have a 2001 2500HD p/u with the 8.1L V8. One thing I have noticed lately is my truck is shifting hard into 2nd gear both up and down. I have noticed that it seems to happen after the transmission reaches operating temp. Anyone have any ideas what might be happening? Also, it is the allison transmission and it doesn't do it everytime.

Thanks