That sounds like the front axle disconnect system is failing.
There is a collar that slides from the drive side to the driven side of the axle shaft that engages the right front axle shaft. That is where the cable comes into play from my previous post.

If the cable does not pull the collar far enough from the drive side to engage the driven side, it will grind the teeth on the driven side. Thereby causing your noise and intermittent 4wd.

Lots of times all of this is due to tranny fluid getting into the vacuum system from the transfer case through the transfer case switch then into the actuator.

The transfer case switch goes bad, sucks in transfer case fluid, loses vacuum when the front axle is engaged and there you go. The front axle only partly engages thus causing the whining sound.

Too much of that whining is going to grind off the teeth on the driven gear and you will need to get a front axle disconnect rebuild kit to fix it, or do the Bravada Axle Swap.

My CrewCab has gone through 4 transfer case switches and the front axle is now to the point I am going to have to rebuild the disconnect. Mine has over 200k miles on it and I don't use 4wd that much so I am getting the stuff to do it and will do it this spring.

Hope this helps...

Bill

 

Thank you Bill. I still have the cable. Do you think changing it will help?

 

Is the transfer case switch that you are referring to, the same as the vacuum actuator?

 

As I previously stated, I would have changed the cable at the same time as the actuator. You already have to disconnect and re connect that cable. The cable is less than $20 and could prevent failures down the road.

Number 2, No. The transfer case switch is screwed into the transfer case housing with three hoses coming from it.

One is from a vacuum source, one goes to the front axle actuator, and the third is a vent tube.

When you shift the transfer case into 4wd this switch takes the vacuum and applies it to the front axle actuator, thus pulling the cable to lock the right front axle shaft.

When you shift from 4wd to 2hi this same switch stops vacuum from going to the front axle actuator and two, it vents the front axle actuator to air, thus allowing the cable to release the right front axle shaft.

As to the question regarding the cable, it couldn't hurt. Doesn't take that long to do anyway. If it doesn't let us know and let's look deeper..

Bill