2000 sierra 1500 4x4 hard shifting problem

[boufa05]

After driving around for about a 1 1/2 hrs the other day. My truck started shifting really hard into 2nd & kinda hard into 3rd.
The next day after sitting over night it shifted normally, but didn't drive long enough to get trans hot. ( i haven't noticed any slipping pior to this problem)
Any idea's as to what is causing this?
Any help would be much appreciated as i'm on a very tight bugdet due to being laid off.
If it helps the truck has 132k on it. About 55k that i've put on it.