'06 RAM 3500 Diesel 6spd clutch/shift problems!

[Charger Man]

Looking for any help on what might be the problem. About 2-3 weeks ago the truck started randomly getting hard to get it in to reverse and some times you had to turn the motor off to get it in reverse. It gradually has gotten worse, and now it is to the point where it won't go in to Rev, 1st, 2nd and sometimes 3rd gear till you turn off the motor. I don't hear any strange noises and I can shift it while moving fine without using the clutch. All fluids are full and clean and the truck only has 66,00 miles on it. Anyone have any help for this one?