I am thinking the Interlock Cylinder is leaking air into the transfer case and venting the air into the front axle s/w on the dash.
If you look in the TM you can see the interlock Cyl. p/n A1-3261-D-290, nsn 2520-01-134-0899
It is located on the top of the transfer case. Little hard to get...
That looks like the same cans that are on the M939 5ton truck. The spring brake diaphragm is #16 and service is #12. Not sure your going to find a complete can. It is not hard to change just need to be safe, cage the brake and open it up, two bolts.
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website like our supporting vendors. Their ads help keep Steel Soldiers going. Please consider disabling your ad blockers for the site. Thanks!