Sorry, this question somehow didn't pop up on my page. I probably get a 2mpg improvement running with the front hubs unlocked. I haven't noticed any movement of the front driveshaft when the hubs are unlocked. At this point I have 53k on the Spyntecs. I've had few issues with the Spyntecs. Recently installed Yukon hubs, replacing the standard Warns. The latter only had one broken engagement ring issue, after which I installed RCVs upgraded drive gears. The Yukons are stronger all around, but I've had some issues with them not wanting to unlock after a trail run. They also required some additional spacer beyond what was supplied by Yukon. They need 11mm total spacer, which leaves 1mm end play on the axle shafts.