Teraflex Dana 44 HD Differential Cover Combo - Includes Pair of Teraflex 3990650 Dana 44 HD Differential Covers Combo includes pair of Teraflex 3990650 HD Dana 44 Differential Covers. Constructed of 3/8" thick ductile iron. Offer extreme protection from rocks, obstacles and other debris on the trail. Include two fill plugs for use in standard or high pinion D44 housings, or when the pinion must be rotated in extreme applications. Fit all Dana 44 housings- standard & high pinion, TeraCRD50R housings.