My buddy has a 2001 3500 dually 4x4 the t case will lock into when you shift it into 4 wheel high of low but the light does not come in in the cluster and the front x wont lock in high or low range makes no difference. It has the manual lever on the floor no push button. is there a actuation solenoid or is it all run off vacuum? any advice would be great thanks in advance.
Garrett

 

The front axle is actuated by vacuum. Check for vacuum at the axle disconnect, and then trace the lines to a switch by the transfer case. I think the light is activated by vacuum as well.

 

Got It Figured Out Found A Cracked Hose Up On The Firewall It Looks As Thought It Is Connected To A Oneway Ck Valve Or Filter Of Some Sort Replaced The Hose And She Locked Right In
Thanks

 

Good to hear it was any easy and inexpensive fix. As far as the light goes for the dash. Down on the CAD Unit on the axle, there are two vacuum lines and two electrical lines for the sensor. Once the fork gets pulled all the way over in the CAD unit, it turns on the light.

 

Just a note for future readeds, sometime the actuators will freeze if you don't use them often(this happen to my truck).