Keep wiggling it, up & down and all around. A little penetrating oil in the snap ring area. It will start moving and when you get it out it will be clean and you'll wonder if it was really necessary. But I would definitely get it out and check it if you've gone this far. There's also a plastic screen in the rear of the transmission. Check that too, much easier than the sump screen. Replace or thoroughly inspect o-rings on plugs. I just did this on our 8110 last week and our 8410 last winter.