You need a new seal, the packing material is the same thing.
https://www.napaonline.com/en/p/NOS11055You can change this in the truck if you are careful. Buy two seals and take one back if you don't need it or get lucky and the first one goes right in. They are really thin and bend easy.
You likely have worn bushings, have a helper turn the wheel back and forth while you watch the pitman arm. If there is side to side movement before twisting movement, the bushings are worn. This will cause any type of seal to leak over time.
Get some Corn Head grease from John deere, it will not leak out and it's cheap. Most any dealer with large equipment will have it. The lawn and garden dealers maybe able to order it in or you can purchase online. One tube is enough for one gear box.
