(Sorry, Title should be 4x4 ACTING Strange)

If I'm driving along in 4x4 and lay into her a bit the 4WD light will start to flicker and eventually go out all together. if I then let off the gas for a few seconds the 4WD light will come back on.

I assume this means I am losing the CAD? As the light directly corresponds to the CAD being engaged/locked? Correct me if im wrong?

I immediately thought vacuum leak at the CAD, so I brought out my vacuum gauge and tested it..I have between -20 and -19.5 in/hg of vacuum at idle....From what Ive read that is normal...so shouldn't my vacuum be fine?..

...Help?




Also, When you pop the shifter into 4H, should the 4WD light light on almost immediately after? Mine takes sometimes 5-10 seconds to come on after I pull the lever...Ive always wondered if this was normal. I dont "Feel" Like im in 4WD until the light comes on.

 

Your vacuums good, but it sounds like the line from the intake manifold to the control switch on the trans. case may be partially plugged. The check valve doesn't seem to be working. Check the line and check valve, repair or replace as needed. Be sure to poke something into the manifold when you pull the hose off to be sure it isn't plugged there.

 

Hi, Thanks for the info, Where exactly is this line located? Are there pictures anywhere?

Thank you.

 

Do you ever lose 4x4 while your are in it?

It takes a while for the light to come on and for it engage sometimes. 5-10 seconds isn't out of the ordinary from what I've seen.

4H shifts easier if you do it while moving. 4L is a different story.

 

I don't actually lose 4x4, the light just starts to flicker and eventually goes out if for example i need to pass someone and apply some gas. Once I let go of the gas or return to Cruising speed the light turns back on.

 

while the CAD controls the engaging and disengaging, of the front axle, there is a sensor on the t-case that sends the signal to the dash cluster, it could be bad, or just loose, or it could be something else entirely.

Are you driving around in 4x4 all the time?

 

No, only where extremely icy, going up hills, etc...Its -30.C here and were in the middle of a blizzard so right now pretty much yes I am using it everywhere. I know its not designed to be used on dry roads.

Could I ask where this sensor is? I will take a look when I get home.

 

The switch for the light in the dash is on the drivers side of the cad housing. I haven't seen any with the switch on the t-case.

If the light is flickering while you are getting on it, even slightly, that means you are losing vacuum at the cad. You have less vacuum to play with when accelerating. I would have a really close look at the check valves up by the intake. (passenger side. should be easy to find.)

Do your vents switch as well when the light flickers?

 

No Actually my vents do not switch when the light flickers, but I do have wild vents, If I really give it the beans mine switch to defrost.

I drove around with a vac gauge attached yesterday and when the light started to flicker I still had around -14 in/hg of vaccum (If that means anything)

Is this the check valve your talking about? (Stole from a thread yesterday)

 

Yep, that would be it. Might be another one as well. Varies from year to year.