I have a late 10K, and both the spindle and back gear are marked "grease". Not knowing any better I greased both of them with teflon grease after I got the lathe - big mistake. While the back gear seems OK with grease, the spindle definitely was not. The grease pretty near locked it up to where it ran full speed even with the bull gear pin pulled, and it also got hot when in back gear. I could not turn the bull gear by hand without also turning the whole spindle. I finally got it freed up by forcing spindle oil into the port marked "grease" until it forced the grease out. Now when I use back gear I lube the spindle with oil - it works fine, no more problems.