i will check today but if i remember correctly mine just had like a T in it but i will look at it in a couple hours and repost this evening

 

Is this line tied to the dipstick for the trans?? Mine has a cap on it and my 4x4 doesn't engage, vacuum always on (can be seen in the actuator). I know chances are the vac switch is bad (already tried 2wd/4wd + trying to move the front driveshaft, all is good).

Would the cap on cause the vacuum to always be on?

Here's what Im talking about :
http://i85.photobucket.com/albums/k7...r/DSCF2885.jpg

 

There should be a Tee and a check valve similar to the one above. Manifold vacuum goes to the larger port on the check valve. One leg of the check goes to the reservoir, one goes to the Tee. Of the two remaining legs of the tee, one goes to the HVAC system and one goes to the 4WD vacuum switch.

Yes, the line is held to the transmission dipstick tube fairly close to the top. The filter looks like a cap but you should be able to blow through it very easily. There is another one right next to where the upper radiator hose connects to the radiator. That filter is the front differential vent.

 

so both of those should be breathers? the one on the fan shroud and the one by the heater hoses? what was i looking for in the check valve? today i jacked up the entire truck put it in 4wd and in drive and the shaft from the xfer case to the front diff was running so i know the xfer case is working and i know the front end is the problem the actuator should that depress all the way or just a little bit?

 

The check valve is the vacuum supply for the HVAC & 4wd systems. If you do not have vacuum to the 4wd system, the front axle will never engage.

 

Yes, both are vents, not check valves. The one by the fan shroud prevents the front differential from building up pressure. The one by the trans dipstick tube vents vacuum in the axle actuator to atmosphere and releases the axle actuator.

The front driveshaft turns whenever the vehicle is in motion, 2WD or 4WD HI, doesn't matter. Driving in 2WD the transfer case is applying power to the front differential however, the power can't get to the ground until the right axle locks in. This is what allows "shift on the fly" into and out of 4WD HI. When you select 4WD HI at the dash switch, the encoder motor moves the linkage inside the transfer case and operates the vacuum switch for the front axle actuator. The right front axle locks up with the differential and the differential is live. This called a mode shift.

Selecting 4WD LO is called a range shift and the vehicle must be stopped while the encoder motor changes the gear range in the transfer case.

EDIT: With the engine running, transmission in PARK, 4WD selected, there should be manifold vacuum at the axle actuator and the cable should pull in about 3/4". When you select 2WD the actuator should release the cable immediately and there should be no vacuum at the actuator.

 

yeah i never have vacuum at the actuator i already tested that out but on that check valve you told me to locate what am i checking for? should my next step be to pull the cover off the front diff? Side note would a bad Wheel Bearing on the passenger side cause this problem? i didn't think it would but just throwing that out there.

 

As you can tell, I'm not an artist, but this should help with the vacuum lines:

 

/\/\ ?

 

A bad wheel bearing will not affect front axle engagement.