USA standard Transfer Case BW4424 Input Shaft. BW4424 T-CASE SEAL INPUT SHAFT .. USA Standard Gear produces top quality transfer case small parts for repair and maintenance, including full top-to-bottom overhauls and rebuilds. USA Standard has one of the largest inventories of OEM and aftermarket transfer case component parts in the industry. Our large inventory and experienced tech support are two of the reasons we have been an industry leading supplier for decades. When you chose our transfer case small parts, you know you're going to get the right part in stock backed by in-house quality assurance testing and expert knowledge.