4wd stopped working on 98 Ram 2500 diesel- what do I look for 1st? Would like to try repair or diagnose before taking to shop. The shifter seems to be engaging but no energy shows up at front tires.

 

Does the 4wd dash light come on? The CAD motor has been a weak spot on Dodges since the 80's...check the vacuum lines for damage from the engine to transfer case then to the CAD motor. If they look good, verify you have vacuum at the shift motor and the transfer case switch is working- if only one hose has vacuum in 2HI and 4HI, the switch is bad. If both get vacuum, the diaphram in the shift motor could be bad, keeping the shift fork and collar in the disengaged position.