AMM82

I'm having some trouble with my 04 Fx4's 4wd. It sounds like it's engaging, but the front tires don't seem to be getting the message. I've checked all the fuses and relays and they're good. What else do I need to check for possible issues?

techrep

iTrader: (1)

the wheel ends or IWE's...barrow a vacuum pump from your local auto parts and test the IWE's...the noise you are hearing is most likely the Transfer case shifting...but the wheel ends are not engaged.

AMM82

I looked at the check valve and it looked like there was some dirt clogging the tubes, could that be why there's not any suction getting through the system?

techrep

iTrader: (1)

if you want them to engage ...they need to vent vacuum...Vacuum holds the wheel ends out...disengaged ...if the vent tubes are blocked then that may be your problem.

wrscpc07

i had to redo my vacuum lines last winter because they were clogged with dirt. Same problem youre having. Used a machine at a shop to test vacuum