1999 dodge ram1500 sport

[Mark1966]

does anyone know why my 4wh light is on when I'm not in 4wh drive can anyone help

[scoutinkeith]

there is a CAD (Central Axle Disconnect) unit on the passanger side of the front axle, when you pull the the T-case into 4wd, a vacume switch on the T-case activates the CAD unit and "locks" together the two pieces of the passanger side axle shaft.
when the locking colar moves, it also contacts the switch for the "4wd" light.
so the problem could be;
1: switch on the cad unit is bad
2: CAD unit is stuck (vac. diafram could be bad)
3: vac switch in T-case not working properly
4: bad connection or broken vac line from T-case to CAD

to start, I"d pull the vac lines from the cad, and check them for vacume. check them in 2wd, and again in 4wd. only one line should have vac at a time.
if the lines coming from the T-case check out, then I'd pull the CAD, and check it. also, before you pull the CAD unit off, it's a good idea to raise the passanger side wheel a little, just to keep oil from leaking out all over the place.

I've seen a diagram on here someplace that shows how the cad unit works, I'll see if I can find it again and post the link for ya.

[scoutinkeith]

here ya go, I found that link that shows how the CAD unit works.
http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm