I believe Kentuck has the right idea, That was the problem in my case anyway. My slip clutches were rusted and siezed. They would slip when loosened way up but when tightened back down the corroded clutch was locked together with no chance of slipping. Yours is newer so may just be to tight. When you see the cost of those shafts you will not be very happy. Here is a link to a web site I bought parts from much cheaper than from dealer. www.drive-lines.com/  Good luck.