My 2000 xterra will not fully engage into 4wd. I can feel it shift, but the front wheels will not lock...

did you turn the locks on the wheels, or check the fuses

Hi Rick:
Depending on the vehicle, there may be externally locking (warn) hubs on the front wheels. These have to be manually dis-engaged at the wheel hubs by rotating a fitting at the center of the hub. Otherwise, there should be a shift lever or switch inside the vehicle that will dis-engage the 4WD

This happened to me. Turn 4 wheel drive on. Than off. Again. On. Than off. This should ding age what you have now

Possible the vacuum bleed-off to the switch you installed isn't allowing it to completely disengage. Pull the bleed-off line from the new switch and see if it works. could be just a tight spot/bent closed in the bleed-off line or the vent plugged.

It's pretty basic actually. The encoder motor engages 4WD within the transfer case which drives the front differential. The drivers side wheel is always engaged at this point and the passengers side wheel is engaged via a vacuum controlled cable (actuator - lunder the battery). There are no "hubs" (so-to-speak), not in the way that you use to see on the older systems where you'd have to lock them.

Hi,
Do you have auto locking hubs on the front wheels, or manual locking hubs?
If you have auto locking hubs chances are they are not engaging properly and will need to be removed and spline sets checked for broken teeth on locking hub and locking shaft.
If you have manual locking hubs then check that they are firm when turning to engage them in the lock position.If they are light when engaging them to the lock position then they my have broken/worn out the locking hub and spline. Also check that the engaging spring inside the hub has enough tension to engage the hubs they may be broken. If the hub are all ok then you have a problem in the transfer box, where the 4WD lever is not meshing the transfer box properly. Hope this helps, let me know how you get on.

Jason

If this is a 2004 Heritage ( old body style ) and the transfer case is known to lock in ( check with truck jacked up, shift into 4WD and try to turn front drive shaft ), the next item to look at is the vacuum disconnect motor for the front axle. This is on the front axle, and will move when shifted into 4WD



It is item #10, on this parts diagram

If you do not have movement in this, check the vacuum lines with a vacuum pressure gauge, to see if vacuum is being applied ( Pink line is 2WD w/ vacuum is operation, Blue line is 4WD w/ vacuum operation ). If no vacuum at the lines, check them back to the vacuum shift solenoids

Sounds like one of your hubs is sticking and not engaging. You can check them by engaging the hubs and the transfer case and jacking up each front wheel independently if it doesn't spin your good, if it does you found your problem. As far as fixing a hub goes, it may be just dry and need some grease, or there are some very good aftermarket hubs available from Warn.
Hope this helps

Lift and support the front of the truck so the front wheels are off the ground.
Key on, engage 4x4 and try to turn the front drive shaft.
If it turns it is a problem with the transfer case.
If it doesn't it is a front axle engagement problem.

When engaging the 4WD system, you are pulling the lever on the Transfer Case right? Not the transmission, it's a different gearbox.
There were several versions of transfer cases that used both full and part-time 4 wheel drive.
From your description this sounds like a part-time transfer case.
Going with that, it is somewhat normal to hear and feel a mild clunk when engaging 4WD high range, especially if you are at a complete stand-still or under full throttle.
Try engaging 4WD High while slowly rolling at idle - no throttle. It should pull in fairly smoothly.
Once 4WD is engaged it will literally LOCK the front and rear axles together. So do not do it on hard dry pavement.
These older style 4WD systems need a little "give" especially when turning. The engineers assume you are not engaging 4WD unless you are in a somewhat slippery scenario.
Many CV joints, axles, U-Joints, differentials, and transfer cases are damaged and broken by folks who don't understand this.
Reading the owners manual should provide a clearer description of what you've got.
Bear in mind that when you come out of 4WD it may not completely release, again due to hard pavement binding up the axles. You can try this: backing up 10-25 feet in a straight line, or getting one set of wheels on the shoulder or in some gravel. That should allow it to release the transfer case and go back to everyday 2WD high.
I hope this helps.
:)