I replaced the battery on my 4066R with an AGM battery. Much better suited to the rough usage of a tractor. Completely sealed. No terminal corrosion, etc. Priced a little higher, but will last longer, plus will not lose charge as quick as a regular battery. My original JD battery only lasted 2 1/2 years and I am already 3 1/2 years into the AGM battery. As best I remember it took a group 34 battery.