my t-case has been grinding on and off for about a year now just driving down the road..well about 2 weeks ago i realized i can grab the spline going into it from the driveshaft and push it up and down about ahalf inch.. what would cause this on an 06 HD? im guessing i do need a new t-case. i bought the truck with 59k last may now i have 98k on it and i use 4wd about 3 times a week. i dont think the other guy used it at all