I've had a similar issue, do as the others have suggested. I will disconnect and pull away from the tiller, pulling the shaft apart, to give yourself more room to work. Mine is tight and difficult to get into if I dont. One thing to keep in mind, make sure you use the stand that holds the tiller up. Mine has fallen on my foot because i did not think to secure it. Luckily the ground was soft at the time and I wasnt injured to bad.
Good luck.