Shaft diameter and slip joints: Since this Bronco will be used hard and has a Cold Duck dual-transfer case setup (which multiplies the torque of the V-8 almost five times before it's transmitted through the driveshafts), we opted for Denny's Heavy-Duty driveshafts. However, the specs are different for the front and rear. Bringhurst prefers to build 2 1/2-inch-diameter driveshafts because he says this yields an extremely strong tube, allowing for an optional longer slip joint. Our front shaft could be only 2 inches in diameter because of space restrictions imposed by the exhaust system. You can see that the maximum extension of the slip yoke is considerably less on the front shaft. The slip joints must be lubed with an extreme pressure grease, not generic chassis grease. Bringhurst says most auto parts stores carry the correct grease, but he sells it if you can't find any locally.