I just tried my loader and I have no fast dump. It shows that I do, but when you move leaver it goes slow, then stops, then further over is slow again. Thats why I think I have something wrong with my spools or something? When they haul my tractor in I am going to get them to check it, because it is annoying to go to dump and hit the spot that it stops and you have to move it less or more to dump! All the way over on my 5035 is no faster then just moving lever an inch or two.
My 2815 works this way too, not sure why but it has been like that since new.I just went out to "play" with the tractor, and couldn't find the collar that you might be talking about. The only thing I can see is the "locking" collar for keeping the handle in a neutral position. I also tried pushing it as far right as it will go. The same thing, the fast dump mode seems to be before all the way right!