It depends on the free-sync implementation of the display, a display can have a 60hz refresh rate, but work up to 75Hz with free-sync
like yours "The maximum refresh rate is less of a concern, but if the pixel response time is too slow then refreshing faster won’t do any good. In the case of the 34UM67 and 29UM67, LG has selected a variable refresh rate range of 48 to 75 Hz. That can be both too high (on the minimum) and too low (on the maximum)." http://www.anandtech.com/show/9118/lg-34um67-ultrawide-freesync-review/2
Oh really? If you try it out do tell me how it works out. I was always kind of annoyed it stopped below ~48 as frame drops will really tear you of a game when it is smooth all the way and the sudden hip, skip and jump.
As for overclocking. Some monitors just don't like it. If you push it past the capability it will either stop working at that refresh rat or just get worse rather than faster.
I have recently bought an LG 29UM68 monitor and it skips frames when set to 75hz. I saw you post and thought that my case could be similar to yours.
My monitor is connected to an AMD HD5750 (soon to be replaced) card through a DisplayPort cable, Freesync is activated from the monitor menu and 75hz is selectable from AMD control center. When I select 75hz i get frame skipping.
I tried overclocking to 61hz with CRU but still no luck, it skips frames. Is my monitor faulty or would a new freesync monitor fix my problem.
Did you select 75hz from control panel when you used your Fury X or just used freesync in games and used 60hz on the desktop? Your experience with the GTX 980TI seems to be exactly like mine with the old Radeon.