916 Front Axle Won't Engage

[Construction]

On my 916 the interaxle differential works, but the front axle doesn't pull. On the transfer case - there is a slight amout of air constantly coming out of the breather fitting. The light comes on an off inside the cab and all sounds normal, but front axle does not pull. Any ideas? Is the constant air out of the diaphram housing normal? or do I have a bad diaphram?

 

[73m819]

should not be air leaking,

 

[Floridianson]

Have you serviced you transfer. Know it's off topic but if you do a service I like to drop the whole fitting off the bottom and there is a screen on the end inside the transfer. I feel it's worth the little extra time just to check it and stick finger in and feel around.
Also off topic but when I got my 920 someone fliped the pump on the transfer and it was pumping the wrong way. When looking at the transfer from the rear the pump will look square with what I will call a little rounded tab on it. That tab should be faceing down. You never know sometimes what someone else has done with these trucks we get.