4wd low but no 4wd high ADVICE NEEDED!

[redshoesyo]

Long story short my 4wd low engages but my 4wd high does not. The dash indicator lights up when switched into 4wd high but there is no affect on the front axle and no sound from the tcase. In snow the rear tires only spin when in 4wd high, ive done a few parking lot test both in and out of the car to confirm this as well as the tests involving having the front jacked up in 4wd and spinning the drive shaft/wheels.

However, when put into 4wd low there is a solid clunk of the transfer case engaging and the system works as it should.

I have checked all fuses and relays, replaced the BCM behind the radio, checked electrical connections at the transfer case and tcase motor and all remains the same.

Any advice on where to go next? What would make 4wd high not work but allow 4wd low to? Any advice is appreciated.

 

[dlynch90]

I had the same problem with mine. I jacked it up in the air, and popped it in 4wd, only rears spin. I unplugged the vacuum lines from the transfer case (passenger side, behind wheel well) and saw they were getting no vacuum. I traced those up to the switch that is inbetween the airfilter and header panel, and unplugged the electrical connector and cleaned it. Plugged it back in, went back down and started getting vacuum. Put it back in 4wd auto, and tires started spinning. Try that, and see what happens. Also make sure that you are getting vacuum to the lines that go from that switch to the vacuum system (the round ball looking thing on the passenger side of the engine compartment).

 

[drdoom]

Also tell us what kind of readings you are getting at the brown wire.