Those cylinders are a true joy to work on. For some unknown reason (unknown to me at least) Mother Deere engineers decided to use a wire ring retainer to hold the gland unit in place, but they decided on a different twist. Instead of just installing it in a groove on the inside of the barrel like most other manufacturers of cylinders do, they put it into another groove on the gland itself. To get the gland, rod, and piston out of the barrel, one must insert a plastic "special tool" into the barrel groove once the gland has been pushed into the barrel deep enough to expose said groove. This "tool" fills the groove so the wire ring can't fall back into it and allows the gland to come out of the barrel. Sometimes.
I've had mixed results with the system, sometimes it works, sometimes not so much. I have a couple of those cylinders in my scrap pile that I was unsuccessful at getting apart after numerous attempts (and a number of plastic tools destroyed). Then a couple weeks ago I did the bucket cylinders on a skidloader. Those came apart correctly. It was no fun, required some effort, granted, but the tools worked and I was able to get them apart.