4wheel drive not engaging
 

1996dodge ram 1500
5.9 liter
170000 miles
So just today my 4x4 is not engaging. Yesterday I used it a bunch but it wouldn't engage today. Sometimes I hear a slight clicking now when I engage it. Also my 4x4switch started flashing on and off then would turn on in 2 wheel then would go off in 4. Any ideas? Thanks

here's how it all works. http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm

the light is controlled by a contact switch on the end of the cad, which is depressed by the collar. several different things can go wrong, including vac lines, electrical switch, wiring, sticky/rusty shaft in the cad diaphragm, burrs on the cad collar.

the best way to troubleshoot it is to put it up on 4 jack stands and operate the truck with engine running so you have vacuum, which is the basis of how it all works.

Ok so I can't jack it tonight but if I'm able to drive then is the wheel turning free or is there still a chance that it is engaging but not moving? ( it seems from that article that is the best because the it is usually vacuum related and not in the transfer case)

i'm not sure i understand the question or not.

as a very quick test, engine off, jack up passenger front ONLY and try to spin the tire. if it spins, then the front axle is NOT engaged, and you have no 4wd.

if its making noise, i'd shift to 2wd and not let if click, thump, or make noise. noise is not good and might be turning a minor problem into a major one.

most 4wd problems are not t-case problems.

Alright I will try tonight And reply on the forum. If it does spin then what's my next thing to look at?

next step is to crank the truck and test for vacuum on the 2 lines at the cad. label them first. you should have vac on one line in 2wd and the other when the t-case shifter is in 4wd.

if vac is wrong, work backwards and fix the vac. if vac is correct, work forwards and fix the CAD.

go ahead and start spraying the 4 little cad bolts with penetrating oil like PB-blaster or other. those little bolts like to break which makes this sucky job even more sucky.

What could be the problem with the cad? Like I don't understand what that does?

take a look at the picture in the .org link above. note that its a 2 piece axle which stays "disengaged" until the collar slides over the splines of both halves, which makes it "engaged". the collar is always on the passenger side outer half, and slides inwards on/off the passenger side inner half.

so the cad is a Rube Goldberg contraption which uses vacuum to push/pull on a rubber diaphragm. which in turns causes a shaft to move back and forth. which has a fork attached to it. which has the collar attached to it. which slides on/off the inner half of the shaft.

the 3 most common problems are:
lack of vacuum. (broken lines)
rusty shaft in the cad.
no engagement due to burrs on the collar/axle splines, or misalignment due to worn bushings.

Don't know if Spicer made some changes in the CAD over the years, but my '95 Dana 44 works just the opposite. That is, the collar rides on the intermediate shaft in 2H and moves to the right to engage the axles in 4H.
The diagram doesn't show it and manuals I've seen don't show it but there is a plastic bushing in the end of the axle that a nub on the intermediate shaft fits into, If it's worn, the axles will be misaligned and the collar can't engage them.

On second look, the diagram has a photo showing where the bushing goes.

my bad, i'm probably wrong about the home position of the collar. i'm sure all years are the same and the parts are all interchangable.

there's actually 2 bushings, (or in some years, one larger bearing and a smaller bushing). the smaller bushing critically aligns the 2 axle halves. the larger bushing (or bearing) is in the inner portion of the axle tube, and anchors the outer end of the inner half of the axle. its not critical for alignment, but does keep things from flopping around.

Where are you OP. got it fixed yet. after you fix it 2 or 3 times and can do it blindfolded, you'll appreciate a posilok. :)