1993 c1500 5.3 swap tranny issues

Ok guys my first post, I use the search a lot but I can't figure this one out. I swapped a 2003 5.3 from a van into my 1993 c1500. I used the original 4l60 cause it had been rebuild with a shift kit. The problem is it seems to stay in first gear along time and when it does shift to second it doesn't downshift back to first when I stop unless I put it in park or reverse. The trans has power and the newer wiring harness. The only thing I can think of now is not having a MAF hooked up is messing with it somehow what do you guys think.