2009 Dodge Ram 1500 won’t go into 4WD

hAD MY RAM 4X4 IN 4 TIMES AS THE SERVE 4 WHEEL DR LIGHT COMES ON AND WON’T GO INTO 4 WHEEL DR. THEY GET A CODE THAT SAYS FRONT DIFF SHIFT PROBLEM AND SAY THEY NEED 4 HRS AT 100 HR TO TRACE DOWN PROBLEM. wITH ALL THE OTHER COMPLAINTS ABOUT SAME ISSUE THEY SHOULD BE ABLE TO FIX THIS. ANYONE EVER GOT THIS FIXED RIGHT?

Lose the all-caps, add some punctuation. and explain who “they” are that need 4 hours of labor to just find the problem.