Installing new oil pan how do you adjust the clearance for the transmission?

The easiest way is to put a straightedge up against the blocks rear surface and bring the pan back until it touches the straight edge. If you are doing this in the vehicle and the transmission is installed simply slide the pan back until it touches the transmission bellhousing and start the bolts that hold the pan on, snug them just until the pan is held securely and install the bolts that hold the transmission and pan together, torque those then torque the ones that secure the pan to the engine.

Hello, I'm Danny.

Here is the torque specifications for the oil pan bolts on your GMC and I've attached below. Always start from the middle and circle your way outward. Hope this helps and thanks again for using 2CarPros.

GM doesn't have a specific pattern for them, once you have the rear bolts in place and torqued down you can use a simple X pattern to tighten them starting in the center and working out, the larger bolts are torqued to 18 ft lb. While the smaller ones are tightened to 106 inch pounds. Basically it's just enough to squeeze the gasket tight. To crack the pan you are going way over the torque spec.