Symptoms -
1. auto-hubs do not lock all the way in. To clarify, I can feel the hubs lock, but once I give it some gas/torque, the front slips out of 4x4.

2. Manual hubs will lock in.

3. Sudden noticable "whine" from front end. Sounds like mudders at 55, but I don't have tires like that. It is definitely based on rotation of the front end. When I hit 35mph the whine shows up, past 45 or so, the whine disappears. Only to return when I slow to stop and the car is passing back through that range.

4. When I turn the key in the ignition without starting the engine and then move the in-cab selector from 2 wheel to 4 wheel, I hear the actuator pump going to town. Most posts here on the forum say the pump should only be working for about 30 seconds to actuate into 4x4. Mine now seems to pump forever. So I was thinking leak, but I took it to a place today to look at it and they said nothing seemed wrong but they felt like they were really unfamiliar with the 4x4 system.

I was stuck recently (in a 4 foot snowdrift) and really gave the 4X4 a workout right before experiencing this problem. Other than that the ball joints were replaced earlier that day, but I am told the hub assembly was not taken apart to replace the joints.

 

The hubs slipping out of 4x4 I would guess a vacum leak or some trashed hubs. is the whine in 4x4 or 2x4 or both? as far as the transfer case issue your gonna have to wait for someone smarter than me. If you want I can find a write up on changing the hubs. whats the info on your truck?

 

Whine is in 2 wheel and 4 wheel and also there in either auto or manual selection on the hub.

 

Get a vacuum guage and hook it into the vacuum line for the hubs. To find the line just look under the fender and over top of the tire. It is straight down. Start the truck and turn the dial. The guage should move. turn the **** again and guage should move.
It will whine if the hubs are not unlocked completely.

 

the hubs must be removed in order to change out the ball joints, they might have screwed up an o ring or the seal that is on the axle behind the hub and the vaccume is leaking.

 

ok so hub hold vacuum, but it seems the line to the driver side hub is not putting out any pressure. I checked line all way back to something that looks like air solenoid. It takes a line in from the vacuum reservoir and a line out to the driver side hub. When I pull this line-in/line out the air is coming in. When I reattach with just the line-in, I get nothing coming out.

Also when I pull the line for the passenger side hub, I get pressure. I have heard people talk here about the vacuum actuator. Anyone know if this is what I am talking about. It has some wire plugged into the top of it and it sits on the fender well right next to the pump and reservoir.

 

PVH (pulse vacuum hublock solenoid) may have a leak in it. The only way I know to fix the pvh is drive a new one under it.
Joe

 

Anyone know a part number I can look for to possibly replace this solenoid.

 

Or even a better question, does anyone know which pins should be getting what type of current on the solenoid end, so I can test and trouble shoot the solenoid?