Raise the vehicle and support it securely on jackstands. Place the transmission in Neutral with the parking brake off. Make reference marks on the driveshaft flange and the pinion flange in line with each other. Remove the rear universal joint nuts and bolts. Turn the driveshaft (or wheels) as necessary to bring the bolts into the most accessible position. If you're working on a model with a two-piece driveshaft, unbolt the center support bearing from the crossmember. Lower the rear of the driveshaft, then slide the front yoke out of the transmission or transfer case. Wrap a plastic bag over the transmission or transfer case housing and hold it in place with a rubber band. This will prevent loss of fluid and protect against contamination while the driveshaft is out. Remove the plastic bag from the transmission or transfer case and wipe the area clean. Inspect the oil seal carefully. Slide the front yoke of the driveshaft into the transmission or transfer case, being careful not to damage the seal in the process. If you're working on model with a two-piece driveshaft, raise the center support bearing into position, install the fasteners and tighten them securely. Raise the rear of the driveshaft into position, checking to be sure the marks are in alignment. If not, turn the rear wheels to match the pinion flange and the driveshaft. Install the new bolts and nuts, tightening them securely. For 4WD models, raise the front of the vehicle and place it securely on jackstands. Remove the skid plate, if equipped. Mark the relationship of the driveshaft to the front differential companion flange and to the transfer case companion flange. Remove the bolts and nuts from the flanges, then lower the shaft from the vehicle. Attach the ends of the shaft to the differential and transfer case companion flanges, install the new bolts and nuts and tighten them securely. Install the skid plate if equipped.