Whats wrong with my truck?

[4x4K10]

Hey guys, i got in my truck tonight after work and started it. The choke usually kicks down after about 5-10 minutes of running. Tonight it took a very long time to kick down. Much longer than usual. This is weird because it's been warm for January these last couple days in New York. So i leave the parking lot to go home and its running normal. In town i went 30-35mph and it was running as it should. I then got to the outskirts of town about 3 miles away from my house and start to go uphill and all of a sudden it feels like my truck is about to die. It will shift into OD but it feels like its barely shifting. When it shifts into OD it sounds like its not firing on all cylinders. I barely made it home, i went about 10-15 the rest of the 3 miles. So what do you think it is? Im guessing the transmission is shot, but i dont think that explains why it wouldnt kick down. I have not had the chance to look at it yet because i just got home. My truck is an 85 k10 305/700r4. Thanks for your help guys.