I have a 2004 fx4 with a 6" lift

I was driving in 2wd with my friend in a muddy area then I went in reverse and drove and hit a bad mud hole and my back tires get stuck and wouldn't go anywhere so I put it in 4wd high and tried going forward and and my back tires spun and the shaft to the front transfer case spun but the tires didn't tried it in 4wd low still didn't work. Also once the RPM's got higher it sounded like a quiet clicking

 

You can hear something like its popping into 4wd but front tires don't spin

 

Probably your IWE or IWE solenoid right above battery! Usually go out and won't activate! Oh and the IWE is integrated wheel end! Basically your 4x4 hub that lock it into 4wd! Usually get crap inside them and freeze up

 

How much should that cost

Earlier I crawled under my truck (turned off) and turned the shaft that goes to the transfer and the axles turned

 

When the truck is started the front axle should not turn IF you IWE solenoid/vac lines are working correctly. When the engine is not running, the front axles should turn because there is no vaccum being applied to the IWE's. Last weekend I had to replace my IWE's because the passenger side would grind while in 2WD and would always stay engaged. The seals were shot so it would not hold vacuum therefore causing it to always be engaged or half engaged causing the grinding sound in 2WD.

 

Thought it work the other way around....truck running create's vac pulls the hubs to unlock when in 2WD. select 4WD vac vents and hub's lock.

 

X2 thats how it does work. The vac keeps the hubs UNLOCKED and when put in 4wd the vac disengages and Locks the hubs

 

Yeah...cause when you have a leak or low vacuum the IWE's try to engauge...(not being held out in 2WD)this is where people hear stuff from the IWE's/hubs.

 

Exactly. When the truck is off the hubs are engaged even if it's in 2wd because there is no vacuum to hold them out

 

Yeah...when the truck is running and you select 4WD in vents the vacuum...if you look at the IWE it has 2 lines.