Got stuck today while hunting. Put truck in 4WD via electronic dash switch. 4x4 HI light comes on but does not really engage. Same thing with LO...light comes on, rear axle gears down, but front axle does not engage.

Front drive shaft does not spin in 4x2, but does spin as it should when switched to 4x4. But it still does not engage- rear wheels spin in mud and front does nothing.

Can not access my lock in hubs without removing after market wheels.

Please help- with suggestions on my problem.

2008 F-250 6.4l diesel V8, four door short bed 4x4.

 

Sooner or later you will have to get at the hubs. Most likely will need replacing. Sounds as if they haven't been accessed, cleaned, or greased lately. A yearly chore by the way.

 

did your hvac default to defrost? If so then your issue is a vacumn leak probably at the hubs.

time to do something about them rims so you can access the hubs and manually turn them.

 

Accessed hubs yesterday. Turned them an have complete 4wd now. Put truck on lift. Without turning hubs, 4x4 switch on dash only engages transfer case and front shaft. Nothing at the wheels.

The small vacuum pump, sitting atop the drivers side engine compartment fuse box, runs constantly and will not shut off unless the key is removed from vehicle. Never noticed before whether it did that or not.

Narrowing this problem down. No breaks in any hoses.

Anyone know about that pump? How often it should be running? Is this the culprit?

 

This sounds to me like a leak in the hubs themselves. If the hoses are good then I would start with some hub maintance.

Pump should not run constant.