I have a 97 Tahoe. It will only shift manually starting in low and moving the lever through all gears. Park to reverse works ok, but park to drive will not let the truck move. It will only move forward when I shift it into low and then manually shift through the gears!

 

does it make a grinding noise when you give it too much gas? i had the same problem in my 97 1500 5.7 with the 4l60e and the forward drive clutch was junk but mine was so bad the grinding vibrated the whole truck horribly