Truck question: 4WD not engaging while moving

[Mark L]

2004 Nissan Titan, 4wd won't engage while moving (it's a knob selector, not a lever), I hear a ratchety sound, like thingy A not fully engaging with thingy B. Works fine when I engage at a stand still. I'm now paranoid about it maybe not disengaging, given a little 'machine noise' when driving. I'm getting worked up over every little sound I hear. Any gearheads suggest what this might be, and how expensive it'll be to fix?

 

[Mark L]

Ooops, Mods please move to Off Topic.

 

[hbar26]

Found this.

http://www.clubtitan.org/forums/13-general-discussion/62771-4-wheel-drive-not-engaging.html

 

[Mountain]

Edit- perhaps the above mentioned problem. If not, check out this:

There is a transfer case servo motor that does the shifting once it receives the signal from the switch / knob. The motor electronics casing had become corroded on our Expedition and it was randomly shifting into 4x4 low. Check connections as well as the motor for function. If the problem is the motor, unlike the $150 part for me the Nissan part will be expen$ive- maybe ~$450 to $500 for aftermarket.

 

[Fixxah]

Had similar problem when I had a shitbox dodge. Vacuum assist shift motor on differential was junk. Then again, it was a dodge, I repeat myself.

 

[JayMcB]

2004 Nissan Titan, 4wd won't engage while moving (it's a knob selector, not a lever), I hear a ratchety sound, like thingy A not fully engaging with thingy B. Works fine when I engage at a stand still. I'm now paranoid about it maybe not disengaging, given a little 'machine noise' when driving. I'm getting worked up over every little sound I hear. Any gearheads suggest what this might be, and how expensive it'll be to fix?

Does it engage if you're not moving? If you can not shift on the fly while moving, but can shift while not moving, it may be the synchro.