Allison External Spin on Filter Service Pack Qty 4 This fits all Allison 1000/2000/2400 Models This filter is mounted to the Outside of the Transmission Case just behind the bell housing. This is a Suggested replacement a minimum of every 5000 miles. If you have any questions, feel free to call us or send us a message. If you need a rebuild kit, internal filter, or other parts for your Allison rebuild please see our store or ask us we will be glad to accommodate all of your part needs.