So I did some searching to try and settle down the mass amount of 4x4 issues and I think this will help 90% of questions and issues!!! ENJOY
The neutral/foot on brake or park is only if you are shifting into 4L. If you are shifting into 4H, applying light throttle up to 55 mph shift on the fly is fine ( per owners manual ).
Operationally vacuum holds the IWE ( Integrated Wheel Ends ) out, and once vac is removed the spring engages the IWE.
Lift and support the front of the truck so the front wheels are off the ground ( take safety precautions, chock wheels, jack stands, etc )
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.
- If the front drive shaft does not turn :
Shut of the truck ( still jacked up, and supported ) remove the vac lines from the IWE. The spring should push the gears in, without the vac line on.
Check the vent line ( tube that is routed into the engine compartment with nothing attached to it ), for blockages.
If the vent line is clear, and with the vac lines off the IWE should be engaged ( both front wheels locked ).
If they lock, the problem is with the IWE solenoid not shutting off vacuum to the IWEs. There is a TSB on the 2004-2006 IWE solenoids, a newer revision has been made, and used from 2007 and newer MYs.
Here is a block diagram of the IWE system
If the front drive shaft turns, I have seen some lightly hit the back of the transfer case, to free up the shift motor, with mixed results.
If you had a vacuum leak, the front wheels would be locked in, or poping in and out of locked in, causing a grinding noise ( IWE gears not engaging fully, grinding the teeth off ).
If you find a problem with the vacuum lines or the IWE solenoids, you can pull the vacuum lines and plug them, this would leave the front wheels locked in all the time. Fine for short use, don't try racing like this ( pushing a dead axle is a lot of HP
The Following User Says Thank You to fx4_soldier For This Useful Post:
I just replaced the solenoid on my truck because it was locking in the hubs while driving down the road... Grinding. So, did the short time that I drove it hurt the gears really bad? Do they need to be replaced? After I replace the solenoid, all is well and 4x4 work fine. But under alot of stress will the gears hold? Thanks, Joe
Thats a tough one, I would be concerned for the gears if you were driving then suddenly your truck is attempting to engage the 4x4. My first step would be to check all the oils for metal shards or shavings and pray you dont find big pieces.
I had a similar issue, I let a friend drive my truck, apparently he was out jumping it or something, and the temperature was close to 0, anyway, he somehow snapped both of the vacuum lines which caused the 4x4 to engage (but no 4x4 light). The next day I had to limp home 200 miles with the hubs locked in. I kept it pretty slow, but had pretty bad vibrations. I sped up to about 60 mph for a bit, and the fluid started bleeding out the overflow. I was trying to troubleshoot it by flashlight, and couldn't get very far, especially since I didn't know the hubs locked in at any loss of vacuum.
I eventually made it home, spent a couple hours reading forums, and 30 seconds the next morning to isolate the problem. I decided to go ahead and change out the transfer case fluid, everything went smoothly, no shavings in it, and no problems since then.
FX4Soldier, I was at Ft Hood on and off for about 15 years before I retired and moved to AL. My folks live in Hermann, MO.
IWE; My truck was doing the intermittant grinding on the front left. Did some troubleshooting and found the vacuum lines were all good (it's NEVER the cheap stuff). My left actuator would disengage but would slowly leak and try to re-engage (the noise). The right would not disengage at all. Yesterday I replaced both actuators. The right one would not even compress by hand. Something in the unit was jammed/blocked internally preventing it mechanically from unlocking on the hub. Lots of tacky black (used to be) grease inside. The left side was less bad, but both showed evidence of water contamination. The next long drive I'll find out if all is well. Only things left that could be bad are the solenoid, the check valve nearest the solenoid, and the vacuum box.
Tools; 5/16 for the actuator bolts
21mm deepwell for the steering & upper control arm nuts
BFH to knock loose the two above items
"normal" metric socket set
I'm only an amateur mechanic, but the IWE replacements are NOT hard to do.