I was just discussing moving the ram on a Bridgeport with a friend. A while back he had problems moving his and about a week ago I needed to move mine, which is an unusual occurrence. I thought that my solution might be of interest here.
The ram just didn't want to move and I was fearful of shearing a drive pin (just guessing that there was something like that in there) between the external lever and internal pinion. I placed a bottle jack between the table and the head and took the load off the slide. That let me squirt some very thin oil in there, It had been lubricated with grease. I then switched to the rear end, where I added a long lump of wood to the jack to reach from floor to slide, and repeated the oil squirting. It still didn't want to move after removing the jack so I jacked up the front again and managed a small movement with the jack in place and the load off. Then I removed the jack and the ram moved OK, albeit a bit stiff. I cycled it fully several times washing the old lubricant off and putting new on. Smooth as silk now, but for how long? If the ram is not moved for a long period the weight gradually squeezes the lubricant out.