My truck won't shift out of 1st but it only happens in 4lo, 4hi 2hi are fine. Is there a switch somewhere for when you shift into 4wd to tell the computer it's in 4lo?
1500 diesel burbs have 8 lugs, the front diff is the 9.25in like all 8 lug trucks, the rear is the 9.5in semi floater used in most 3/4 ton gas trucks, 2500 burbs got the 10.5 14bff.