I have a '13 and am getting the classic symptoms of this... started stuttering a bit at 85K but didn't think much of it. Started showing the full ugly symptoms with the hard clunk on turning and the bang on reverse at around 130k . I found the part on line and with shipping it was $713. Local dealer wanted close to $900. They are replacing it for $250. Next payday I may buy another one just to have it on handHello all!
For those with AWD and experience clunking (engaging/disengaging) when making a turn from a complete stop, your wheels are rotating at a different rate of speed. The feedback from the wheel hub speed sensors/encoders are telling the computer this and the rear engages/disengages as if there's loss of traction. From what I've learned, having owned my SFS 2.0T for over 2 years now and a viscous coupler blown (replaced under warranty), I can tell you a few things to look for.
Basic funtionality: The drive shaft from the front differential to the rear differential is rotating full time. The viscous coupler in between the shaft and the rear diff and engages when the computer sends a signal to the actuator between zero and 40 mph. Over time, the internals get sloppy and ultimately fail. I suspect it's like a lovejoy coupler with a rubber boot between the two mating surfaces. Look it up in google images if you're curious. It's my best guess that if my theory is correct, this boot wears out, breaks apart-whatever, and then there's excessive play between the 3 fingers on each side that union. One good high torque engagement and boom, there goes the coupler! Part costs like $750 from the dealer and the parts department told me they always keeps one in stock because they are constantly replacing them. I know this to be the weak link of all 2013, 2014, 2015, 2016, 2017 DM Santa Fe Sport all wheel drive AWD drivetrain. (added for better indexing for search engines)
Bought used 42k miles, and returned to dealer to complain about clunking when making a hard turn 90 degrees from a stop. Nothings wrong they said. Time progressed and around 75k, roads were wet and lost traction when taking off. Boom! I knew it was toast. FWD only. Returned to dealer and confirmed what I knew. Replaced in like 1.5 hours. Warranty deductible of $50 and out the door.
With a fresh viscous coupler, the bumping/clunking I described was no longer happening. Now that my odometer is @ 92k, I'm starting to notice it again. Beware AWD SFS's! Otherwise, great car but put together with plastic pins and everything else plastic. Life cycle could be 30-40k miles depending on driving habits. I'm not easy on mine. Hope this helps somebody! BTW, I have no intention of following up on this thread to answer questions. If you ask, someone else in the community will need to chime in. I did this simply because info is limited and wanted to provide my experience and feedback on this.