Craftsman Tiller Worm Gear 917-04381 Genuine OEM Replacement Fits Craftsman MTD Troybilt Ace Kmart. This is a Genuine OEM Craftsman part. This worm gear (part number 917-04381) is for tillers. Worm gear 917-04381 attaches inside the gear case and drives the shaft to turn the wheels. Wear work gloves to protect your hands when installing this part. ... - Craftsman Tiller Worm Gear 917-04381 Genuine OEM Replacement Fits Craftsman MTD Troybilt Ace Kmart.