My son's '98 4 wheel drive does not work. I have replaced the actuator, still nothing.

Any Ideas as to what I might try next? It goes into the 4hi, 4 low etc, just no movement out of the front end.

 

Have you actually removed the CAD and checked the operation? I'm guessing thats what you mean when you say actuator. If it shifts but nothing happens you should look over the vacuum lines.

 

Does the light illuminate on the dash to indicate you are actually in 4 wheel drive or are you referring to the manual shifter for the transfer case? If you are reffering to the transfer case then you are only engaging the transfer case until the light illuminates indicating that the CAD(central axle disconnect) has engaged the slip ring on the axle shaft in the front. As Keegan said check on the back side of the front axle where you will see a device mounted to the axle. That is the CAD. See if a vacuum line is off or broken. It could be anywhere along those lines.

 

check for vac on the 2 lines between t-case and CAD.
should be vac on one when in 2wd and on the other in 4wd.

next most common problem is corrosion on the little internal shaft in the cad.
http://www.dodgeram.org/tech/repair/..._engagment.htm

 

If you decide to check the vacuum , it should be at or about 15psi. If it's not, you have a bad hose or the next thing to try would be the vacuum switch on top of the TC.

I almost forgot, there are check valves on 2 of the hoses that could be bad. And if you have an odd heat issue and/or cruise control does not work(if it has) they are also sources of a vacuum leak.